Qore Programming Language Reference Manual: Operators

Qore Programming Language Reference Manual 0.8.11

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Operators

The following table lists all Qore operators in order of precedence, starting with the highest precedence. The lower the precedence number, the higher the precedence, therefore the operators with precedence level 1 (`"{}"`, `"[]"`, `"."`) have the highest precedence of all Qore operators. The precedence levels in Qore are roughly equal to the precedence levels of C language operators. To explicitly specify the precedence for expression evaluation, use parentheses `()`.

Operators

Operator | Prec. | Description | Example
`` | `1` | backquote/backtick operator | `ls -l`
{} | `1` | hash element or object member expression dereference operator | $hash{"na" + "me"}
. | `1` | hash element or object member literal dereference operator | $hash.name $obj.method()
[] | `1` | list element, string, and binary dereference operator | $list[1]
++ | `2` | pre-increment operator | ++$a
++ | `2` | post-increment operator | $a++
-- | `2` | pre-decrement operator | --$a
-- | `2` | post-decrement operator | $a--
new | `3` | class instantiation/new object operator | new Socket()
background | `3` | background/thread creation operator | background mainThread()
delete | `3` | delete operator | delete $var
remove | `3` | remove operator | remove $var
cast<>() | `3` | cast<>() operator | cast<SubClass>($var)
! | `4` | logical negation operator | if (!($a > 10)) {}
~ | `5` | binary not/bit inversion operator | $var = ~$var
- (unary minus) | `6` | unary minus operator | $var = -$var
shift | `7` | shift list element operator | shift $list
pop | `7` | pop list element operator | pop $list
chomp | `7` | chomp end-of-line character operator | chomp $string
trim | `7` | trim characters operator | trim $string
elements | `8` | number of elements operator (list, hash, string, binary) | elements $list
keys | `8` | hash key list operator | keys $hash
* | `9` | multiplication operator | $var = $a * 10
/ | `9` | division operator | $var = $a / 10
% | `10` | modula operator | $var = $a % 10
+ | `11` | plus operator: string, binary, list, and hash concatenation, integer and float addition | $a + 10 "hello" + "there" $list + "new value" $hash + ( "newkey" : 100 )
- | `11` | minus operator (arithmetic subtraction, hash key removal) | $a - 10
>> | `12` | bitwise shift right operator | 0xff00 >> 8
<< | `12` | bitwise shift left operator | 0xff00 << 8
exists | `13` | exists value operator | exists $var
instanceof | `13` | instanceof class operator | instanceof Qore::Mutex
< | `14` | Logical less than operator | $a < 10
> | `14` | Logical greater than operator | $a > 10
== | `14` | Logical equality operator | $a == 10
!= | `14` | logical inequality operator | $a != 10
<= | `14` | Logical less then or equals operator | $a <= 10
>= | `14` | logical greater than or equals operator | $a >= 10
<=> | `14` | logical comparison operator | $a <=> $b
=== | `14` | absolute logical equality operator | $a === 10
!== | `14` | absolute logical inequality operator | $a !== 10
=~ // | `14` | regular expression match operator | $a =~ /text/
!~ // | `14` | regular expression no match operator | $a !~ /text/
=~ s/// | `14` | regular expression substitution operator | $a =~ s/text/text/
=~ x// | `14` | regular expression pattern extraction operator | $a =~ x/(\w+):(\w+)/
=~ tr | `14` | transliteration operator | $a =~ tr/a-z/A-Z/
& | `15` | bitwise/binary AND operator | $a & 0xff
| | `15` | bitwise/binary OR operator | $a | 0xff
^ | `15` | bitwise/binary XOR operator | $a ^ 0xff
&& | `16` | logical AND operator | ($a = 1) && ($b < 10)
|| | `16` | logical OR operator | ($a = 1) || ($b < 10)
? : | `17` | conditional operator | $a == 2 ? "yes" : "no"
, | `18` | comma operator | 1, 2, 3, 4, 5
unshift | `19` | unshift list element operator | unshift $list, $val
push | `19` | push list element operator | push $list, $val
splice | `19` | splice list or string operator | splice $list, 2, 2, (1, 2, 3)
extract | `19` | extract list or string operator | my $sublist = extract $list, 2, 2, (1, 2, 3)
map | `19` | map operator | map $closure($1), $list
foldl | `19` | fold left to right operator | foldl $closure($1 - $2), $list
foldr | `19` | fold right to left operator | foldr $closure($1 - $2), $list
select | `19` | select elements from list operator | select $list, $1 > 1
= | `20` | assignment operator | $var = 1
+= | `21` | plus-equals (add-to) operator | $var += 5
-= | `21` | minus-equals (subtract-from) operator | $var -= 5
&= | `21` | and-equals operator | $var &= 0x2000
|= | `21` | or-equals operator | $var |= 0x2000
%= | `21` | modula-equals operator | $var %= 100
*= | `21` | multiply-equals operator | $var *= 10
/= | `21` | divide-equals operator | $var /= 10
^= | `21` | xor-equals operator | $var ^= 0x2000
<<= | `21` | shift-left-equals operator | $var <<= 0x2000
>>= | `21` | shift-right-equals operator | $var >>= 0x2000

Note
  All Qore operators perform thread-atomic actions with respect to the immediate arguments of the operator. If the operators are used in a complex expression, the entire expression is not thread-atomic unless explicit user-level locking is used. For example: `$a += 5` is a thread-atomic action, but `$a += $b–` is not atomic, but rather made up of two atomic actions.
  When an operator taking more than one argument is used with arguments of different data types, Qore automatically converts one or both data types to a data type supported by the operator in order to evaluate the result, according to the precedence lists given for each operator. That is; when an operator operates on mixed types, the types listed first in the following sections have precedence over types listed farther down in the lists. The result type will always be equal to the final operation type after any conversions due to type precedence per operator. If no type of either argument matches a supported data type for the operator, both types will be converted to the highest precedence data type for the operator and then the operator will evaluate the result. For explicit type conversion, please see the boolean(), string(), date(), int(), float(), etc functions.

# Backquote Operator (``)

Synopsis
  Executes the shell command in a separate process and returns the stdout as a string. To perform the same action using a Qore expression, see the backquote() function.

Syntax
  ```shell_command```

Return Type
  string

Example
  my string $dir = `ls -l`

Arguments Processed by ``

Argument | Returns | Processing
unquoted string shell_command | string | The shell command will be executed and the `stdout` is returned as a string

Exceptions

  BACKQUOTE-ERROR | An error occurred in fork() or creating the output pipe

# Hash Element or Object Member Expression Dereference Operator ({})

Synopsis
  Retrieves the value of hash key or object member by evaulating an expression.

Syntax
  container_expression `{` expression `}`

Return Type
  any

Example
  printf("%s\n", $hash{getName()});

Arguments Processed by {}

Argument | Processing
container_expression | This expression must evaluate to a hash or an object; if not, the operator returns no value (NOTHING)
expression | - list: if the expression evaluates to a list, then a slice of the hash or object is returned as a hash containing keys given in the list that are present in the hash or object. If the key as given in the list (converted to a string if necessary) is not present in the hash or object, then it is also not present in the hash returned; of none of the given keys exist in the hash, an empty hash is returned. - anything other than list: the expression is converted to a string (if necessary); the value of the hash key corresponding to this string will be returned; if the key or member does not exist, then no value is returned

Exceptions

  PRIVATE-MEMBER | Attempt to access a private member outside the class

# Hash Element or Object Member Literal Dereference Operator (.)

Synopsis
  Retrieves the value of a hash key or object member using a literal identifier or an expression.

Syntax
  hash_or_object_expression `.` identifier
  object_expression `.` method_name``([args ...]`)`
  hash_or_object_expression `.` expression

Return Type
  any

Example
  printf("%s\n", $hash.name);
  $obj.method("argument");

Arguments Processed by . (hash key or object member literal dereference)

Argument | Processing
hash_or_object_expression | This expression must evaluate to a hash or an object; if not, then the operator returns no value
identifier | An unquoted string taken as the literal name of the hash key or object member. If no such key exists, then no value is returned. In order to use hash keys that are not valid Qore identifiers, please use the {} operator. If the member is a private member and access is made outside the class, a run-time exception will be thrown. Also note that constants or static class member names will not be resolved, in this case the string given is used as the literal name of the hash key or object member

Arguments Processed by . (object method call)

Argument | Processing
object_expression | The object_expression must evaluate to an object or a run-time exception is thrown
method_name`([`args`])` | If the method does not exist in the class a run-time exception is thrown. Otherwise the method is called with any optional arguments given and the return value of the method is returned.

Arguments Processed by . (hash key or object member expression dereference)

Argument | Processing
hash_or_object_expression | This expression must evaluate to a hash or an object; if not, then the operator returns no value
expression | - list: if the expression evaluates to a list, then a slice of the hash or object is returned as a hash containing keys given in the list that are present in the hash or object. If the key as given in the list (converted to a string if necessary) is not present in the hash or object, then it is also not present in the hash returned; of none of the given keys exist in the hash, an empty hash is returned. - anything other than list: the expression is converted to a string (if necessary); the value of the hash key corresponding to this string will be returned; if the key or member does not exist, then no value is returned

Exceptions

  PRIVATE-MEMBER | Attempt to access a private member outside the class
  METHOD-DOES-NOT-EXIST | Attempt to access a method not defined for this class
  METHOD-IS-PRIVATE | Attempt to access a private method from outside the class
  BASE-CLASS-IS-PRIVATE | Attempt to access a method of a privately-inherited base class from outside the class
  OBJECT-METHOD-EVAL-ON-NON-OBJECT | Attempt to execute a method on a non-object

# List, String, and Binary Dereference Operator ([])

Synopsis
  Retrieves the value of a list element, the given character of a string, or the integer value of a byte for a binary object. If the index value is not valid for the argument, NOTHING is returned. Note that this operator only works as a list dereferencing operator in lvalue expressions; you cannot assign a character or a byte value to strings or binaries using this operator.

Syntax
  list_expression`[`offset_expression``] string_expression`[`offset_expression``] binary_expression`[`offset_expression``]

Return Type
  any

Example
  printf("%s\n", $list[2]);
  printf("%s\n", $str[2]);
  printf("0x%x\n", $binary[2]);

Arguments Processed by []

Argument | Processing
list_expression | If the expression evaluates to a list, then the offset_expression will be used to return the given element from the list
string_expression | If the expression evaluates to a string, then the offset_expression will be used to return the given character from the list; note that multi-byte characters with UTF-8 are properly respected with this operator
binary_expression | If the expression evaluates to a binary, then the offset_expression will be used to return the integer value of the byte given from the binary object
offset_expression | The expression is evaluated and converted to an integer if necessary. Then the value of the given element given is returned according to the type of the first expression (as listed above; elements start at position 0)

This operator does not throw any exceptions; if the first expression does not evaluate to either a list, string, or binary, then no value (NOTHING) is returned.

# Pre-Increment Operator (++)

Synopsis
  Increments an lvalue and returns the incremented value; only works on integer and floating-point values.

Syntax
  `++`lvalue

Return Type
  int or float

Example
  ++$i;

Arguments Processed by ++ (pre-increement)

Argument | Processing
Float | increments lvalue and returns the result
Integer (or any other type) | First converts the value of lvalue to an integer if necessary, then increments lvalue and returns the result

This operator does not throw any exceptions.

# Integer Post-Increment Operator (++)

Synopsis
  Increments an integer or floating-point lvalue and returns the value before the increment; if the lvalue is neither a floating-point value or an integer, it will be converted to an integer

Syntax
  lvalue`++`

Return Type
  any

Example
  $i++;

Arguments Processed by ++ (post-increment)

Argument | Processing
Float | saves the value of the lvalue as the result, then increments lvalue, then returns the saved original value of lvalue
Integer (or any other type) | saves the value of the lvalue as the result, then converts the value of lvalue to an integer if necessary and increments it, then returns the saved original value of lvalue

This operator does not throw any exceptions.

# Integer Pre-Decrement Operator (--)

Synopsis
  Decrements an lvalue and returns the incremented value; only works on integer and floating-point values.

Syntax
  `–`lvalue

Return Type
  int or float

Example
  --$i;

Arguments Processed by – (pre-decrement)

Argument | Processing
Float | increments lvalue and returns the result
Integer (or any other type) | First converts the value of lvalue to an integer if necessary, then increments lvalue and returns the result

This operator does not throw any exceptions.

# Integer Post-Decrement Operator (--)

Synopsis
  Decrements an integer or floating-point lvalue and returns the value before the decrement; if the lvalue is neither a floating-point value or an integer, it will be converted to an integer

Syntax
  lvalue`–`

Return Type
  any

Example
  $i–;

Arguments Processed by – (post-decrement)

Argument | Processing
Float | saves the value of the lvalue as the result, then decrements lvalue, then returns the saved original value of lvalue
Integer (or any other type) | saves the value of the lvalue as the result, then converts the value of lvalue to an integer if necessary and decrements it, then returns the saved original value of lvalue

This operator does not throw any exceptions.

# New Object Operator (new)

Synopsis
  Creates an instance of a class by running the class' constructor on the new class (if any exists) and returns the new object.
  Note that if possible it is normally better to declare an object with its type and use the abbreviated form to construct the object as follows:
  my Mutex $m();
  This provides type information to the parser which allows more errors to be caught at parse time (instead of at run time), and furthermore allows Qore to improve performance by performing more work once at parse time rather than for every time the object is accessed at run time (for example, method and variant resolution), and normally requires less typing.

Syntax
  `new` class_identifier`(`constructor_args ...`)`

Return Type
  an object of the specific class given

Example
  my Mutex $obj = new Qore::Mutex();

Arguments Processed by new

Argument | Processing
class_identifier | The class_identifier must be an existing class name; if so, the operator instantiates an object of this class, executes the constructor for the class (if any exists, along with any base class constructors, if applicable) on the new object, and returns the object (for constructor execution order in an inherited class, see Class Inheritance). If an exception is thrown in the constructor, the object is deleted immediately.

Note
  See class documentation for possible exceptions

# Background Operator (background)

Synopsis
  Start a background thread and return the TID (thread ID).

Note
  - expressions that have no effect cannot be used with the background operator (a parse exception will be thrown)
  - it is illegal to make changes to a local variable anywhere in a background expression (a parse exception will be thrown)
  - local variables and find expressions are evaluated before the new thread is started and the result of the evaluation is used in the expression in the new thread
  - it is not possible to pass local variables by reference anywhere in a background expression (a parse exception will be thrown)

Syntax
  `background` expression

Return Type
  int

Example
  my int $tid = background startThread();

Arguments Processed by background

Argument | Processing
expression | The expression given as an argument will be executed in a new thread. The TID of the new thread will be returned as the return value of the operator

Exceptions

  THREAD-CREATION-FAILURE | If the thread table is full or if the operating system returns an error while starting the thread, this exception is thrown

# Delete Operator (delete)

Synopsis
  The delete operator deletes the contents of an lvalue. If the delete operator is called on an object, the object will be destroyed unconditionally. The delete operator does not return any value.
  When called on a hash key, the key is removed from the hash entirely; when called on a list element, the element is assigned NOTHING (i.e. the list size does not change).
  The delete operator will delete multiple keys from a hash (i.e. delete a slice from a hash) when called on a hash dereferenced by a list of strings, giving the keys to delete (see example below).
  In the case the delete operator operates on an object, any exception can be thrown that is thrown by the class' destructor.
  For a similar operator that returns the value that is removed from the data structure, and does not delete objects, see the remove operator.

Syntax
  `delete` lvalue_expression

Return Type
  Does not return any value

Example
  # delete a single key from a hash
  delete $value;
  # delete multiple values from a hash
  delete $h.("a", "b", "c");

This operator does not throw any exceptions, however exceptions could be thrown in an object's destructor method when deleted by this operator.

# Remove Operator (remove)

Synopsis
  The remove operator removes a value from a data structure, or, in the case the operand of the remove operator is a simple value, the value itself is removed from the variable and returned. The remove operator returns the value removed from the lvalue.
  When called on a hash key, the key is removed from the hash entirely, and the value returned is the value of the key removed from the hash; when called on a list element, the element is assigned NOTHING (i.e. the list size does not change).
  The remove operator will remove and return a slice from a hash when called on a hash dereferenced by a list of strings, giving the keys to remove (see example below).
  The remove operator does not call destructors when operating on objects, but if removing an object from an lvalue or from a data structure within the lvalue causes the object to go out of scope, it will be destroyed, and then its destructor could throw an exception.
  For a similar operator that deletes the value that is removed from the data structure, see the delete operator.

Syntax
  `remove` lvalue_expression

Return Type
  any

Example
  # remove a single value from a hash
  my any $var = remove $hash.value;
  # remove a slice from a hash
  my hash $nh = remove $h.("a", "b", "c");

This operator does not throw any exceptions, however exception could be thrown in an object's destructor if it goes out of scope due to the action of this operator.

# Cast Operator (cast<>())

Synopsis
  The cast<>() operator provides a way to tell the parser that the type of object is not actually the declared type but rather a subclass as given between the angle brackets.

Syntax
  `cast`<class_identifier`>(`object_expression`)`

Return Type
  the specific class given

Example
  cast<SubClass>($obj).method();

Arguments Processed by cast<>()

Argument | Processing
class_identifier | This must be a literal unquoted string giving a class name or a namespace-qualified path to a class (ex: `Namespace::MyClass`)
object_expression | This must be an expression that evaluates to an object that can be cast to the given class; this is mostly useful at parse time to avoid non-existent-method-call warnings

Exceptions

  RUNTIME-CAST-ERROR | The expression given does not evaluate to an object that can be cast to the given class

# Logical Not Operator (!)

Synopsis
  Reverses the logical sense of an expression (True becomes False and False becomes True).

Syntax
  `!`expression

Return Type
  bool

Example
  if (!exists $error_code)
  do_something();

Arguments Processed by !

Argument | Processing
expression | The expression is evaluated and converted to a bool, if necessary. Then the value is logically reversed (True becomes False, False becomes True)

This operator does not throw any exceptions.

# Binary Not Operator (~)

Synopsis
  The value of each bit in an integer is reversed (0 becomes 1, 1 becomes 0).

Syntax
  `~`expression

Return Type
  int

Example
  $a = ~$b;

Arguments Processed by ~

Argument | Processing
expression | The argument is converted to an integer (if necessary), and bitwise negation is performed on the argument (ex: `666 & ~27` results in `640`)

This operator does not throw any exceptions

# Unary Minus Operator (-)

Synopsis
  Changes the sign of numeric values.

Syntax
  -expression

Return Type
  int or float

Example
  $a = -$b;

Arguments Processed by - (unary minus)

Argument | Processing
Float | Gives the negative of its argument as a Float (ex: `-(-1.1) = 1.1, -(1.1) = -1.1`
Integer | Gives the negative of its argument as an Integer (ex: `-(-1) = 1, -(1) = -1`

This operator does not throw any exceptions

# Shift Operator (shift)

Synopsis
  Removes the first element from a list and returns that element.

Syntax
  `shift` lvalue

Return Type
  any

Example
  my *string $a = shift $ARGV;

Arguments Processed by shift

Argument | Processing
lvalue | Returns the first element of the list, and the list is modified by having the first element removed from the list. If the lvalue is not a list, no action is performed and the operator returns no value (NOTHING)

This operator does not throw any exceptions.

# Pop Operator (pop)

Synopsis
  Removes the last element from a list and returns that element.

Syntax
  `pop` lvalue

Return Type
  any

Example
  $a = pop $list;

Arguments Processed by pop

Argument | Processing
lvalue | Returns the last element of the list, and the list is modified, having the last element removed from the list. If the lvalue is not a list, no action is performed and the operator returns no value (NOTHING)

This operator does not throw any exceptions.

# Chomp Operator (chomp)

Synopsis
  Removes the end-of-line marker(s) (`'\n'` or `'\r\n'`) from a string, or each string element in a list, or each hash key value in a hash (if the value is a string) and returns the number of characters removed.
  To perform this operation on a non-lvalue expression, see the chomp() function.

Syntax
  `chomp`lvalue

Return Type
  int

Example
  chomp $str;

Arguments Processed by chomp

Argument | Processing
lvalue (String) | Removes any EOL characters from a string and returns the number of characters removed.
lvalue (List) | Removes any EOL characters from each string element of the list passed and returns the number of characters removed.
lvalue (Hash) | Removes any EOL characters from each hash key's value (where the value is a string) and returns the number of characters removed.

This operator does not throw any exceptions.

# Trim Operator (trim)

Synopsis
  Removes whitespace characters from the beginning and end of a string, or each string element in a list, or each hash key value in a hash (if the value is a string) and returns the value processed (string, list, or hash).
  To perform this operation on a non-lvalue expression, see the trim() function.
  The following whitespace characters are removed from the beginning and end of strings: `' '` (blank spaces), `'\n'`, `'\r'`, `'\t'`, `'\v'` (vertical tab, ASCII 11), and `'\0'` (null character).

Syntax
  `trim` lvalue

Return Type
  string, list, or hash

Example
  trim $str;

Arguments Processed by trim

Argument | Processing
lvalue (String) | Removes whitespace characters from the beginning and end of a string and returns the value processed.
lvalue (List) | Removes whitespace characters from the beginning and end of each string element of the list passed and returns the list.
lvalue (Hash) | Removes whitespace characters from the beginning and end of each string value of the hash passed and returns the hash.

This operator does not throw any exceptions.

# Map Operator (map)

Synopsis
  Executes (or maps) an expression on a list and returns the result. An optional select expression can be given to filter elements out from the result list.
  If the second argument (list_expression) is an object inheriting the AbstractIterator class, the `map` operator iterates the object by calling AbstractIterator::next(), and the implicit argument `$1` in the map_expression and any optional select_expression is the value returned by AbstractIterator::getValue().
  If the second argument is not a list or an object inheriting AbstractIterator, then map_expression is executed on the single value and the result is returned, and any select_expression is ignored.

Return Type
  any

Syntax
  `map` map_expression, list_expression [, select_expression]

Examples
  # returns (2, 4, 6)
  my list $l = map $1 * 2, (1, 2, 3);
  # prints out the keys of a hash; one to a line
  map printf("%s\n", $1), $hash.keyIterator();

Arguments Processed by map

Argument | Processing
map_expression | The expression to map on the list; the implicit argument `$1` represents the current element being processed (or the object itself if the `map` operator is iterating an object inheriting the AbstractIterator class).
list_expression | The data to process; if this is not a list then the map_expression is run on the single argument passed, unless the map_expression is an object inheriting the AbstractIterator class; in this case the `map` operator iterates the object by calling AbstractIterator::next()
[select_expression] | An optional expression than can be used to filter out elements of the list before the map expression is applied; if this expression evaluates to False on an element, then the element will be skipped and the map_expression will not be applied on that element.

This operator does not throw any exceptions (however note that exceptions could be thrown by expressions executed by this operator).

Since
  Qore 0.8.6.2 the map operator when used with an AbstractIterator object instantiates the value returned by AbstractIterator::getValue() instead of the iterator itself

# Fold Left Operator (foldl)

Synopsis
  Folds an operation on a list from left to right and returns the result. The result of each individual operation is used as the first argument in the foldl expression for the next element in the list. The first operation of the fold is made by executing the fold expression on the first and second elements of the list, from this point onwards, the result of each successive operation is used as the first argument for the next operation, the second argument being the next element in the list.
  If the second argument (list_expression) is an object inheriting the AbstractIterator class, the `foldl` operator iterates the object by calling AbstractIterator::next(), and the implicit arguments `$1` and `$2` in expression are the container values returned by AbstractBidirectionalIterator::getValue(). If the list_expression does not evaluate to a list or an object inheriting AbstractIterator, then the evaluated argument is returned immediately with no processing by the fold expression.

Syntax
  `foldl` expression, list_expression

Return Type
  any

Examples
  The following returns `foldl` expression returns `5`
  my int $result = foldl $1 - $2, (10, 4, 1);
  The following `foldl` expression joins a list with `", "` or returns a single argument (if the second operand is not a list)
  my string $str = foldl $1 + ", " + $2, $list;

Arguments Processed by foldl

Argument | Processing
expression | The expression to fold on the list; the implicit argument `$1` represents the result of the last operation (or the first element in the list when beginning the fold), and `$2` represents the next element of the list.
list_expression | The list, AbstractIterator object or other value according to the rules above to process

This operator does not throw any exceptions (however note that exceptions could be thrown by expressions executed by this operator).

# Fold Right Operator (foldr)

Synopsis
  Folds an operation on a list from right to left and returns the result. The result of each individual operation is used as the first argument in the foldr expression for the next element in the list in reverse order. The first operation of the right fold is made by executing the fold expression on the last and penultimate elements of the list, from this point onwards, the result of each successive operation is used as the first argument for the next operation, the second argument being the next element in the list in reverse order.
  If the second argument (list_expression) is an object inheriting the AbstractBidirectionalIterator class, the `foldr` operator iterates the object by calling AbstractBidirectionalIterator::prev(), and the implicit arguments `$1` and `$2` in expression are the container values returned by AbstractBidirectionalIterator::getValue(). If the list_expression does not evaluate to a list or an object inheriting AbstractBidirectionalIterator, then the evaluated argument is returned immediately with no processing by the fold expression.

Syntax
  `foldr` expression, list_expression

Return Type
  any

Example
  # returns -13
  foldr $1 - $2, (10, 4, 1);

Arguments Processed by foldr

Argument | Processing
expression | The expression to fold on the list; the implicit argument `$1` represents the result of the last operation (or the last element in the list when beginning the fold), and `$2` represents the next element of the list in reverse order.
list_expression | The list, AbstractIterator object or other value according to the rules above to process

This operator does not throw any exceptions (however note that exceptions could be thrown by expressions executed by this operator).

# Select From List Operator (select)

Synopsis
  Selects elements from a list that meet the given criteria and returns the new list.
  If the first argument (list_expression) is an object inheriting the AbstractIterator class, the `select` operator iterates the object by calling AbstractIterator::next(), and the implicit argument `$1` in expression is the value returned by AbstractIterator::getValue(); in this case the operator always returns a list (which may be empty if expression returns False for all elements in the iterator object or if the iterator object is empty), and the value of the object in the list returned is the value returned by AbstractIterator::getValue().
  If the list expression does not evaluate to a list or an object inheriting AbstractIterator, then the select expression is evaluated using the value of the list expression as an argument, if it evalutes to true, then the value is returned, otherwise, no value is returned.

Syntax
  `select` list_expression, expression

Return Type
  any

Example
  # returns (2, 4, 6)
  select (1, 2, 3, 4, 5, 6), !($1 % 2);

Arguments Processed by select

Argument | Processing
list_expression | The list to process or an object inheriting AbstractIterator
expression | The expression will be evaluated on each element of the list, the implicit argument `$1` represents current element of the list (or the iterator object itself when list_expression is an object inheriting AbstractIterator); only if the expression evaluates to True will the element appear in the result list

This operator does not throw any exceptions (however note that exceptions could be thrown by the expression executed by this operator).

Since
  Qore 0.8.6.2 the map operator when used with an AbstractIterator object instantiates the value returned by AbstractIterator::getValue() instead of the iterator itself

# Elements Operator (elements)

Synopsis
  Returns the number of elements in a list, the number of keys in a hash, the number of characters (not bytes) in a string, or the number of bytes in a binary object.

Syntax
  `elements` expression

Return Type
  int

Example
  my int $size = elements $list;

Arguments Processed by elements

Argument | Processing
expression list | Returns the number of elements in the list
expression hash | Returns the number of keys in the hash
expression string | Returns the number of characters in the string (which may be different than the number of bytes for multi-byte character encodings such as `UTF-8`
expression binary | Returns the number of bytes in the binary object

This operator does not throw any exceptions.

See Also
  <value>::size()

# Keys Operator (keys)

Synopsis
  Returns a list representing the keys in a hash.

Syntax
  `keys` hash_expression

Return Type
  list or NOTHING

Example
  foreach my string $key in (keys $hash)
  printf("%s = %s\n", $key, $hash.$key);

Arguments Processed by keys

Argument | Processing
hash_expression | Returns a list of strings giving the keys in hash_expression, which must evaluate to a hash. If not, then no value is returned.

This operator does not throw any exceptions.

See Also
  - <hash>::keys()
  - <object>::keys()

# Multiply Operator (*)

Synopsis
  Multiplies two arguments.

Syntax
  expression1 `*` expression2

Return Type
  int, float, or number

Example
  $value = $x * $y;

Arguments Processed by * (in order of precedence)

Argument | Processing
number | Gives the result of multiplying its arguments; ints and floats are converted to numbers if at least one of the arguments is a number
float | Gives the result of multiplying its arguments; ints are converted to floats if at least one of the arguments is a float
int | Gives the result of multiplying its arguments
any other type | Converts argument to a number and performs the multiplication

This operator does not throw any exceptions.

# Divide Operator (/)

Synopsis
  Divides a number by another.

Syntax
  expression1 `/` expression2

Return Type
  int, float, or number

Example
  $value = $x / $y;

Arguments Processed by / (in order of precedence)

Argument | Processing
number | Gives the result of dividing its arguments; ints and floats are converted to numbers if at least one of the arguments is a number
float | Gives the result of dividing its arguments; ints are converted to floats if at least one of the arguments is a float
int | Gives the result of dividing its arguments
any other type | Converts argument to a number and performs the division

Exceptions

  DIVISION-BY-ZERO | division by zero error

# Modula Operator (%)

Synopsis
  Gives the integer remainder after division of one number by another.

Syntax
  expression1 `%` expression2

Return Type
  int

Example
  $mod = $x % $y;

Arguments Processed by %

Argument | Processing
int | Gives expression1 modula expression2 (ex: `12 % 10` result in `2`). Arguments are converted to integers if necessary.

This operator does not throw any exceptions.

# Plus (Addition and Concatentation) Operator (+)

Synopsis
  Numeric addition, list, string, binary, and hash concatenation operator.

Syntax
  expression1 `+` expression2

Return Type
  int, float, number, date, list, string, binary, or hash

Example
  $a = 1 + 2;
  $string = "hello" + "-there";
  $list = (1, 2) + ("three", "four", "five");
  $hash = ( "key1" : 1, "key2" : 2) + ( "key3" : "three", "key4": "four");
  $bin = $bin1 + $bin2;

Arguments Processed by + (in order of precedence)

Argument | Processing
list list | Gives the result of concatenating its arguments, i.e. `(1, 2) + (3, 4) = (1, 2, 3, 4)`
string | Gives the result of concatenating its arguments
date | Gives the result of adding date/time values (see Date/Time Arithmetic)
number | Gives the result of adding its arguments
float | Gives the result of adding its arguments
int | Gives the result of adding its arguments
hash | Gives the result of concatenating/merging its arguments. Any common keys will be overwritten by the values in the second hash (expression2)

This operator does not throw any exceptions.

# Minus Operator (-)

Synopsis
  With float, integer, or number arguments, subtracts one number from another.
  With date arguments, subtracts one date from another; if both date arguments are absolute dates, the result is a relative date (duration) giving the time between them; if the first date argument is an absolute date and the second is a relative date (duration), then the result is an absolute date. If both date arguments are relative dates, then the result is a relative date. If the first argument is a relative date and the second date is an absolute date, the result is an absolute date as if the operands were reversed.
  However, if the left-hand side is a hash, and the right-hand side is a string, then the hash key represented by the string will be removed from the hash. If the left-hand side is a hash and the right-hand side is a list, then each element in the list will be converted to a string and any hash key with that name will be deleted from the hash.

Syntax
  expression1 `-` expression2

Return Type
  int, float, number, date, or hash

Example
  $num = $x - $y;
  $date = 2010-05-13 - P3MT14H10M;
  $hash = $hash - "key";
  $hash = $hash - ("key1", "key2", "key3");

Arguments Processed by - (in order of precedence)

Argument | Processing
date | date subtraction: expression1 - expression2
number | arithmetic subtraction: expression1 - expression2
float | arithmetic subtraction: expression1 - expression2
int | arithmetic subtraction: expression1 - expression2
hash - string | hash key deletion: expression1 - expression2
hash - list | hash key deletion: expression1 - expression2; all elements of the list are converted to strings (if necessary) and any keys with those names are deleted from the hash.

This operator does not throw any exceptions.

# Shift Right Operator (>>)

Synopsis
  Shifts bits in an integer towards zero (divides an integer by a power of 2)

Syntax
  expression1 `>>` expression2

Return Type
  int

Example
  $a = $x >> $y;

Arguments Processed by >>

Argument | Processing
int | Gives the result of shifting expression1 right by expression2 bits. Arguments are converted to integers if necesssary.

This operator does not throw any exceptions.

# Shift Left Operator (<<)

Synopsis
  Shifts bits in an integer towards infinity (multiplies an integer by a power of 2)

Syntax
  expression1 `<<` expression2

Return Type
  int

Example
  $a = $x << $y;

Arguments Processed by <<

Argument | Processing
int | Gives the result of shifting expression1 left by expression2 bits. Arguments are converted to integers if necessary.

This operator does not throw any exceptions.

# Class Instance Operator (instanceof)

Synopsis
  Tests if an expression is an instance of a given class or not.

Syntax
  expression `instanceof` class_identifier

Return Type
  bool

Example
  if ($obj instanceof Qore::Mutex)
  print("object is Mutex\n");

Arguments Processed by instanceof

Argument | Processing
expression | If expression is an instance of the named class, then the operator returns True, otherwise returns False. The operator will return True if the class is a base class, also even if it is privately inherited.

This operator does not throw any exceptions.

# Exists Operator (exists)

Synopsis
  Tests if an expression represents a value or not.

Syntax
  `exists` expression

Return Type
  bool

Example
  if (exists $a)
  printf("a = $n\n", $a);

Arguments Processed by exists

Argument | Processing
expression | If expression evaluates to a value, then the operator returns True, otherwise returns False.

This operator does not throw any exceptions.

# Less Than Operator (<)

Synopsis
  Tests if a value is less than another; types are converted if necessary (ex: `("1" < 2)` is True).

Syntax
  expression1 < expression2

Return Type
  bool

Example
  if ($x < $y)
  printf("%n is less than %n\n", $x, $y);

Arguments Processed by < (in order of precedence)

Argument | Processing
number | If expression1 is numerically less than expression2, returns True, otherwise returns False
float | If expression1 is numerically less than expression2, returns True, otherwise returns False
int | If expression1 is numerically less than expression2, returns True, otherwise returns False
string | If expression1 comes before expression2 in string sort order, returns True, otherwise returns False
date | If expression1 is before (or a shorter amount of time than of the arguments are Relative Date/Time Values (Durations)) expression2, returns True, otherwise returns False

This operator does not throw any exceptions.

# Greater Than Operator (>)

Synopsis
  Tests if a value is greater than another; types are converted if necessary (ex: `("2" > 1)` is True).

Syntax
  expression1 > expression2

Return Type
  bool

Example
  if ($x > $y)
  printf("%n is less than %n\n", $x, $y);

Arguments Processed by > (in order of precedence)

Argument | Processing
number | If expression1 is numerically greater than expression2, returns True, otherwise returns False
float | If expression1 is numerically greater than expression2, returns True, otherwise returns False
int | If expression1 is numerically greater than expression2, returns True, otherwise returns False
string | If expression1 comes after expression2 in string sort order, returns True, otherwise returns False
date | If expression1 is after expression2, returns True, otherwise returns False

This operator does not throw any exceptions.

# Equals Operator (==)

Synopsis
  Tests if a value is equal to another; types are converted if necessary (ex: `("1" == 1)` is True). For absolute equals, where types must also be equal to return true, see the Absolute Equals Operator (===).

Syntax
  expression1 == expression2

Return Type
  bool

Example
  if ($x == $y)
  printf("%n is equal to %n\n", $x, $y);

Arguments Processed by == (in order of precedence)

Argument | Processing
string | If expression1 is equal to expression2, returns True, otherwise False
number | If expression1 is equal to expression2, returns True, otherwise False
float | If expression1 is equal to expression2, returns True, otherwise False
int | If expression1 is equal to expression2, returns True, otherwise False
date | If expression1 is equal to expression2, returns True, otherwise False
list | If each element in the each list where order is relevant satisfies this operator, the operator returns True, otherwise it returns False
hash | If each hash has the same keys and the value of each equal key in each hash satisfies this operator, the operator returns True, otherwise it returns False
binary | If expression1's memory contents and size are equal to expression2's, then returns True, otherwise False
object | If expression1 is a reference to the same object as expression2, then returns True, otherwise False
NULL | If both expressions are NULL, returns True, otherwise returns False
NOTHING | If neither expression has a value, returns True, otherwise returns False

This operator does not throw any exceptions.

# Not Equals Operator (!=)

Synopsis
  Tests if a value is not equal to another; types are converted if necessary (ex: `("1" != 1)` is False).

Syntax
  expression1 != expression2

Return Type
  bool

Example
  if ($x != $y)
  printf("%n is not equal to %n\n", $x, $y);

Arguments Processed by != (in order of precedence)

Argument | Processing
string | If expression1 is not equal to expression2, returns True, otherwise False
number | If expression1 is not equal to expression2, returns True, otherwise False
float | If expression1 is not equal to expression2, returns True, otherwise False
int | If expression1 is not equal to expression2, returns True, otherwise False
date | If expression1 is not equal to expression2, returns True, otherwise False
list | If each element in the each list where order is relevant satisfies this operator, the operator returns True, otherwise it returns False
hash | If the hashes have different keys or the value of each equal key in each hash satisfies this operator, the operator returns True, otherwise it returns False
binary | If expression1's memory contents or size are not equal to expression2's, then returns True, otherwise False
object | If expression1 is not a reference to the same object as expression2, then returns True, otherwise False
NULL | If either expressions is not NULL, returns True, otherwise returns False
NOTHING | If one of the expressions has a value, returns True, otherwise returns False

This operator does not throw any exceptions.

# Less Than Or Equals Operator (<=)

Synopsis
  Tests if a value is less than or equals to another value; types are converted if necessary (ex: `("1" <= 2)` is True).

Syntax
  expression1 <= expression2

Return Type
  bool

Example
  if ($x <= $y)
  printf("%n is less than or equal to %n\n", $x, $y);

Arguments Processed by <= (in order of precedence)

Argument | Processing
number | If expression1 is numerically less than or equal to expression2, returns True, otherwise returns False
float | If expression1 is numerically less than or equal to expression2, returns True, otherwise returns False
int | If expression1 is numerically less than or equal to expression2, returns True, otherwise returns False
string | If expression1 comes before in string sort order or is the same as expression2, returns True, otherwise returns False
date | If expression1 is before or is the same exact date and time as expression2, returns True, otherwise returns False

This operator does not throw any exceptions.

# Greater Than Or Equals Operator (>=)

Synopsis
  Tests if a value is greater than or equals to another value; types are converted if necessary (ex: `("2" >= 1)` is True).

Syntax
  expression1 >= expression2

Return Type
  bool

Example
  if ($x >= $y)
  printf("%n is greater than or equal to %n\n", $x, $y);

Arguments Processed by >= (in order of precedence)

Argument | Processing
number | If expression1 is numerically greater than or equal to expression2, returns True, otherwise returns False
float | If expression1 is numerically greater than or equal to expression2, returns True, otherwise returns False
int | If expression1 is numerically greater than or equal to expression2, returns True, otherwise returns False
string | If expression1 comes after in string sort order or is the same as expression2, returns True, otherwise returns False
date | If expression1 is after or is the same exact date and time as expression2, returns True, otherwise returns False

This operator does not throw any exceptions.

# Comparison (<=>) Operator

Synopsis
  Tests if the left-hand value is less than, equal, or greater than the right-hand value; types are converted if necessary (ex: ("1" <=> 2) returns -1).

Syntax
  expression1 <=> expression2

Return Type
  int

Example
  switch ($x <=> $y) {
  case -1:
  print("$x is less than $y\n");
  break;
  case 0:
  print("$x is equal to $y\n");
  break;
  case 1:
  print("$x is greater than $y\n");
  break;
  }

Arguments Processed by <=> (in order of precedence)

Argument | Processing
string | If expression1 comes after in string sort order as expression2, returns `1`, otherwise if they are equal, returns `0`, otherwise if expression1 comes before expression2, returns `-1`
number | If expression1 is numerically greater than expression2, returns `1`, otherwise if they are equal returns `0`, otherwise returns `-1`
float | If expression1 is numerically greater than expression2, returns `1`, otherwise if they are equal returns `0`, otherwise returns `-1`
int | If expression1 is numerically greater than expression2, returns `1`, otherwise if they are equal returns `0`, otherwise returns `-1`
date | If expression1 is after expression2, returns `1`, otherwise if they are equal returns `0`, otherwise returns `-1`

This operator does not throw any exceptions.

# Absolute Equals Operator (===)

Synopsis
  Checks two values for equality without doing any data type conversions; if the types do not match, then the result is False.

Syntax
  expression1 === expression2

Return Type
  bool

Example
  if ($x === $y)
  printf("%n is equal to %n and has the same data type as well\n", $x, $y);

Arguments Processed by ===

Argument | Processing
All | This operator returns True only if the types and values of both sides of the operator are exactly equal, otherwise returns False. No type conversions are done.

This operator does not throw any exceptions.

# Absolute Not Equals Operator (!==)

Synopsis
  Checks two values for inequality without doing any data type conversions. If the data types do not match, then returns True.

Syntax
  expression1 !== expression2

Return Type
  bool

Example
  if ($x !== $y)
  printf("%n is not equal to %n and may not have the data type as well\n", $x, $y);

Arguments Processed by !==

Argument | Processing
All | This operator returns True if either the types or the values of the arguments are different, otherwise it retuns False. No type conversions are done.

This operator does not throw any exceptions.

# Regular Expression Match Operator (=~)

Synopsis
  Checks for a regular expression match; returns True if the expression matches the string, False if not. See regex_options for the meaning of the `i`, `s`, `x`, and `m` options after the regular expression.
  See Regular Expressions for more information about regular expression support in Qore.

Syntax
  expression `=~ [m]/`regex`/[isxm]`

Return Type
  bool

Example
  if ($str =~ /hello/)
  printf("%s contains 'hello'\n", $str);

Arguments Processed by =~

Argument | Processing
string | This operator returns True if the regular expression in regex matches the string in expression.

This operator does not throw any exceptions.

# Regular Expression No Match Operator (!~)

Synopsis
  Checks for a regular expression non match; returns True if the expression does not match the string, False if it does. See regex_options for the meaning of the `i`, `s`, `x`, and `m` options after the regular expression.
  See Regular Expressions for more information about regular expression support in Qore.

Syntax
  expression `!~ [m]/`regex`/[isxm]`

Return Type
  bool

Example
  if ($str !~ /hello/)
  printf("%s does not contain 'hello'\n", $str);

Arguments Processed by !~

Argument | Processing
string | This operator returns True if the regular expression in regex does not match the string in expression.

This operator does not throw any exceptions.

# Regular Expression Substitution Operator

Synopsis
  Looks for a regular expression match in a string, and, if found, substitutes the matched string with a new string. Subpattern backreferences are supported in the target string, `$1`=first subpattern, `$2`=second subpattern, etc... See regex_options for the meaning of the `i`, `s`, `x`, and `m` options after the regular expression.
  See Regular Expressions for more information about regular expression support in Qore.

Syntax
  lvalue `=~ s/`regex_pattern`/`target_string`/[isxmg]`

Return Type
  string or NOTHING (if the lvalue does not hold a string)

Example
  $str =~ s/hello/goodbye/i;
  $str =~ s/(\w+) +(\w+)/$2, $1/;

Arguments Processed by =~ s///

Argument | Processing
string | This operator substitutes text in the lvalue string if the regular expression matches. Subpattern backreferences are supported in target_string, `$1`=first subpattern, `$2`=second subpattern, etc..

This operator does not throw any exceptions.

# Regular Expression Pattern Extraction Operator

Synopsis
  Matches regular expression patterns (enclosed in parentheses) in a string and returns a list giving the text matched for each pattern. If the regular expression does not match, then no value (NOTHING) is returned. See regex_options for the meaning of the `i`, `s`, `x`, and `m` options after the regular expression.
  See Regular Expressions for more information about regular expression support in Qore.

Syntax
  string `=~ x/`regex_with_patterns`/[isxm]`

Return Type
  list or NOTHING (if the lvalue does not hold a string or if the pattern is not matched)

Example
  $list =~ x/(\w+):(\w+)/;
  $list =~ x/(.*)\.(.*)/;

Arguments Processed by =~ x//

Argument | Processing
string | This operator extracts strings from string based on patterns enclosed in parentheses in the regular expression.

This operator does not throw any exceptions.

# Transliteration Operator

Synopsis
  Makes character substitutions in an lvalue; character ranges can also be used.

Syntax
  lvalue `=~ tr/`source_chars`/`target_chars`/`

Return Type
  string or NOTHING (if the lvalue does not hold a string)

Example
  $str =~ tr/a-z/A-Z/;

Arguments Processed by =~ tr//

Argument | Processing
string | This operator substitutes characters in the lvalue string. Note that if there are more characters in source_chars than in target_chars, then the last character in target_chars will be used for any source matches where the source character position is greater than the length of target_chars.

This operator does not throw any exceptions.

# Bitwise/Binary And Operator (&)

Synopsis
  Performs a bitwise (binary) AND operation on two integers.

Syntax
  expression1 & expression2

Return Type
  int

Example
  $a = $x & $y;

Arguments Processed by &

Argument | Processing
int | Gives the result of the binary (bitwise) AND operation between expression1 and expression2 (ex: `0xffb2 & 0xa1 = 0xa1`); operands are converted to integers if necessary.

This operator does not throw any exceptions.

# Bitwise/Binary Or Operator (|)

Synopsis
  Performs a bitwise (binary) OR operation on two integers.

Syntax
  expression1 | expression2

Return Type
  int

Example
  $a = $x | $y;

Arguments Processed by |

Argument | Processing
int | Gives the result of the binary (bitwise) OR operation between expression1 and expression2 (ex: `0xb001` | `0xfea = 0xbfeb`); operands are converted to integers if necessary

This operator does not throw any exceptions.

# Bitwise/Binary Xor Operator (^)

Synopsis
  Performs a bitwise (binary) XOR operation on two integers.

Syntax
  expression1 ^ expression2

Return Type
  int

Example
  $a = $x ^ $y;

Arguments Processed by ^

Argument | Processing
int | Gives the result of the binary (bitwise) EXCLUSIVE OR operation between expression1 and expression2 (ex: `0xaef1 & 0xfb32 = 0x55c3`); operands are converted to integers if necessary

This operator does not throw any exceptions.

# Logical And Operator (&&)

Synopsis
  Checks to see if two expressions are True with logical short-circuiting.

Syntax
  expression1 && expression2

Return Type
  bool

Example
  if ($x && $y)
  printf("%n and %n are both True\n", $x, $y);

Arguments Processed by &&

Argument | Processing
bool | Returns True if both expressions are True, False if otherwise. Logical short-circuiting is implemented; if expression1 is False, then expression2 is not evaluated, and the operator returns False.

This operator does not throw any exceptions.

# Logical Or Operator (||)

Synopsis
  Returns True if either of the arguments are True with logical short-circuiting.

Syntax
  expression1 || expression2

Return Type
  bool

Example
  if ($x || $y)
  printf("either %n or %n or both are True\n", $x, $y);

Arguments Processed by ||

Argument | Processing
bool | Returns True if either or both expressions evaluate to True, False if otherwise. Logical short-circuiting is implemented; if expression1 is True, then expression2 is not evaluated, and the operator returns True.

This operator does not throw any exceptions.

# Conditional Operator (? :)

Synopsis
  Evaluates and returns the value of one of two expressions depending on the value of a conditional expression.

Syntax
  expression ? if_true_expression : if_false_expression

Return Type
  any

Example
  $a = ($z > 100 ? "Big" : "Small");

Arguments Processed by ? :

Argument | Processing
All | If expression is evaluated to be True, then the if_true_expression is evaluated and returned. Otherwise the if_false_expression is evaluated and returned.

This operator does not throw any exceptions.

# Comma Operator (,)

Synopsis
  Makes a list from more than one element.

Syntax
  expression1, expression2

Return Type
  list

Example
  $a = 1, 2, "three";

Arguments Processed by ,

Argument | Processing
All | The comma operator builds lists of arguments

This operator does not throw any exceptions.

# Unshift Operator (unshift)

Synopsis
  Inserts an element into the first position of a list and moves all other elements up one position.

Syntax
  `unshift` lvalue, expression

Return Type
  any

Example
  unshift $list, "one";

Arguments Processed by unshift

Argument | Processing
All | Inserts the value of expression as the first element in the list given by lvalue. All other elements in the list are moved forward.

# Push Operator (push)

Synopsis
  Adds one element to the end of a list and returns the list processed (or NOTHING if the lvalue is not a list).

Syntax
  `push` lvalue, expression

Return Type
  list or NOTHING (if the lvalue is not a list)

Example
  push $list, "last";

Arguments Processed by push

Argument | Processing
All | Appends the value of the expression as the last element in the list given by lvalue. If expression evaluates to a list, this list will be appended as the last element of lvalue. To concatenate lists, use the plus operator.

# Splice Operator (splice)

Synopsis
  Removes and optionally inserts elements in lists, strings, and binary objects and returns the lvalue after processing. For a similar operator that returns the values removed, see the extract operator.
  Works on strings, lists, and binary data in a similar way; removes elements from a list, characters from a string, or bytes from binary data and optionally inserts new ones. If no length_expression is given, splice removes all elements/characters/bytes from the list, string, or binary data lvalue starting at offset_expression (offsets begin at 0). Otherwise, a number of elements/characters/bytes equal to length_expression is removed (or up to the end of the list/string/data if applicable). If substitution_expression is present, then the removed elements/characters/bytes are substituted with the elements/string/bytes given by this expression.
  Note that string splice takes character offsets, which may not be the same as byte offsets for multi-byte character encodings, such as `UTF-8`

Syntax
  `splice` lvalue, offset_expression, [length_expression, [substitution_expression]]

Return Type
  list, string, or binary (returns lvalue after processing)

Example
  splice $list, 2, 2;
  splice $string, 2, 2, "-text-";
  splice $bin, 2, 2, <deadbeef>;

Arguments Processed by splice

Argument | Processing
lvalue (list, string, or binary) | If the lvalue is a list, list elements are processed, if it is a string, characters in the string are processed, and for binary data, bytes are processed. For any other data type, no action is taken.
offset_expression | The start element/character/byte position for removing elements/characters/bytes from the list, string, or binary data; if this value is negative, it gives the element offset from the end of the data
length_expression | The number of elements/characters/bytes to remove. If this expression is not present, then all elements/characters/bytes from the offset to the end of the list/string/binary data are removed. If this expression is present and evaluates to 0, no characters/elements/byte are removed; if this value is negative, then it gives an offset from the end of the data (ie -2 means remove all elements/characters/bytes up to but not including the last two)
substitution_expression | For list splice, an optional element or list to substitute for the removed elements (to insert a list in a single element's position, make sure that the list to be inserted is the first and only element of another list used as the argument in this position; in other words, pass a list within a single-element list). For string splice, an optional string to substitute for the removed characters. For binary splice, string or binary data to substitute for any removed bytes.

# Extract Operator (extract)

Synopsis
  Removes and optionally inserts elements in lists and strings. For a similar operator that removes values from an lvalue and returns the lvalue (instead of the value removed), see the splice operator.
  Works on either strings, lists, and binary data in a similar way; removes elements from a list, characters from a string, and bytes from binary data and optionally inserts new ones. If no length_expression is given, extract removes all elements/characters/bytes from the lvalue starting at offset_expression (offsets begin at 0). Otherwise, a number of elements/characters/bytes equal to length_expression is removed (or up to the end of the data if applicable). If substitution_expression is present, then the removed elements/characters/bytes are substituted with the data given by this expression.
  When operating on lists, a list is returned of any elements extracted (if no elements are extracted, then an empty list is returned); when operating on strings, a string is extracted of all characters extracted from the string (if no characters are extracted, then an empty string is returned). When operating on binary data, a binary object is returned.
  Note that string extract takes character offsets, which may not be the same as byte offsets for multi-byte character encodings, such as `UTF-8`

Syntax
  `extract` lvalue, offset_expression, [length_expression, [substitution_expression]]

Return Type
  list, string, or binary (the value(s) removed from lvalue)

Example
  my list $sublist = extract $list, 2, 2;
  my string $substring = extract $string, 2, 2, "-text-";
  my binary $b = extract $bin, 2, 2, <deadbeef>;

Arguments Processed by extract

Argument | Processing
lvalue (list, string, or binary) | If the lvalue is a list, list elements are processed, if it is a string, characters in the string are processed, and for binary data, bytes are processed. For any other data type, no action is taken.
offset_expression | The start element/character/byte position for removing elements/characters/bytes from the list, string, or binary data; if this value is negative, it gives the element offset from the end of the data
length_expression | The number of elements/characters/bytes to remove. If this expression is not present, then all elements/characters/bytes from the offset to the end of the list/string/binary data are removed. If this expression is present and evaluates to 0, no characters/elements/byte are removed; if this value is negative, then it gives an offset from the end of the data (ie -2 means remove all elements/characters/bytes up to but not including the last two)
substitution_expression | For list extract, an optional element or list to substitute for the removed elements (to insert a list in a single element's position, make sure that the list to be inserted is the first and only element of another list used as the argument in this position; in other words, pass a list within a single-element list). For string splice, an optional string to substitute for the removed characters. For binary splice, string or binary data to substitute for any removed bytes.

# Assignment Operator (=)

Synopsis
  Assigns a value to an lvalue and returns the value assigned.

Syntax
  lvalue `=` expression

Return Type
  any

Example
  $a = 1;

Arguments Processed by =

Argument | Processing
All | Assigns the value of expression to lvalue

# Plus Equals Operator (+=)

Synopsis
  Increments and concatentates an lvalue with the value of an expression depending on the data type of the lvalue, unless the lvalue is NOTHING, in which case this operator acts like the assignment operator (simply assigns the value of the right hand side to the lvalue).

Syntax
  lvalue `+=` expression

Return Type
  int, float, number, date, list, string, binary, hash, or object

Example
  $a += 10;
  $date += P1M2DT45M;
  $list += $new_element;
  $string += ".foo";
  $binary += <0c67a374>
  $hash += ("new-key" : 1, "other" : "two");
  $object += $hash;

Arguments Processed by +=

Argument | Processing
lvalue (list) | the expression will be evaluated and concatenated to the lvalue. If expression is a list, the lists will be concatenated, to ensure adding a single element to a list, use the push operator
lvalue (hash or (object) | the expression will be evaluated, and, if it is a hash or object, then it's members will be added to the lvalue, any duplicate elements in the lvalue will be overridden by elements in the expression.
lvalue (string) | the expression will be evaluated and converted to a string if necessary and concatenated to the lvalue.
lvalue (number) | the expression will be evaluated and converted to a number if necessary and added to the lvalue.
lvalue (float) | the expression will be evaluated and converted to a float if necessary and added to the lvalue.
lvalue (binary) | the expression will be evaluated and converted to a binary if necessary and added to the lvalue.
lvalue (date) | the expression will be evaluated and converted to a date if necessary and added to the lvalue.
lvalue (NOTHING) | the lvalue will be assigned to the value of expression.
lvalue (all other types) | the lvalue's type will be converted to an integer, and the expression will be evaluated and converted to an integer if necessary, and then the result will be added to the lvalue.

# Minus Equals Operator (-=)

Synopsis
  For a float or integer argument, decrements the value of an lvalue by the value of an expression. However if the lvalue is a hash or object and the expression is a string, removes the key represented by the string from the hash or object.

Syntax
  lvalue `-=` expression

Return Type
  int, float, number, date, hash, or object

Example
  $a -= 10;
  $date -= PT45H213S;
  $hash -= "key";
  $hash -= ("key1", "key2");
  $object -= "key";
  $object -= $list_of_keys;

Arguments Processed by -=

Argument | Processing
lvalue (number) | the expression will be evaluated and converted to a number if necessary and subtracted from the lvalue
lvalue (float) | the expression will be evaluated and converted to a float if necessary and subtracted from the lvalue
lvalue (date) | the expression will be evaluated and converted to a date if necessary and subtracted from the lvalue
lvalue (hash or (object), expression (string) | the hash key represented by expression will be removed from the lvalue
lvalue (hash or (object), expression (list) | each element in the list will be converted to a string (if necessary) and the key represented by each string will be removed from the hash or object
lvalue (NOTHING), expression (any type) | the expression will be assigned to lvalue
lvalue (all other types) | the lvalue's type will be converted to an integer (if necessary), and the expression will be evaluated and converted to an integer (if necessary), and then the result will be subtracted from the lvalue

# And Equals Operator (&=)

Synopsis
  Performs a bitwise (binary) AND operation on an lvalue using the value of an expression and returns the new value.

Syntax
  lvalue `&=` expression

Return Type
  int

Example
  $a &= 0xfe;

Arguments Processed by &=

Argument | Processing
All | the lvalue's type will be converted to an integer if necessary, and the expression will be evaluated and converted to an integer as well if necessary, and then the result will be binary and'ed to the lvalue

# Or Equals Operator (|=)

Synopsis
  Performs a bitwise (binary) OR operation on an lvalue using the value of an expression and returns the new value.

Syntax
  lvalue `|=` expression

Return Type
  int

Example
  $a |= 0xba;

Arguments Processed by |=

Argument | Processing
All | the lvalue's type will be converted to an integer if necessary, and the expression will be evaluated and converted to an integer as well if necessary, and then the result will be binary or'ed to the lvalue

# Modula Equals Operator (%=)

Synopsis
  Performs a modula calculation on an lvalue using the value of an expression and returns the new value.

Syntax
  lvalue `%=` expression

Return Type
  int

Example
  $a %= 100;

Arguments Processed by %=

Argument | Processing
All | the lvalue's type will be converted to an integer if necessary, and the expression will be evaluated and converted to an integer as well if necessary, and then the result will be used to divide the lvalue's value and the remainder will be saved to the lvalue

# Multiply Equals Operator (*=)

Synopsis
  Performs a multiplication operation on an lvalue using the value of an expression and returns the value assigned.

Syntax
  lvalue `*=` expression

Return Type
  int, float, or number

Example
  $a *= 10;

Arguments Processed by *=

Argument | Processing
All | The type precedence from highest to lowest is number, float float, and int, other types are converted to int. The expression will be evaluated and multiplied by the lvalue, and the result will be saved to the lvalue.

# Divide Equals Operator (/=)

Synopsis
  Performs a division operation on an lvalue using the value of an expression and returns the value assigned.

Syntax
  lvalue `/=` expression

Return Type
  int, float, or number

Example
  $a /= 10;

Arguments Processed by /=

Argument | Processing
All | The type precedence from highest to lowest is number, float float, and int, other types are converted to int; The expression will be evaluated and multiplied by the lvalue, and the result will be saved to the lvalue. The expression will be evaluated and used to divide the lvalue, and the result will be saved to the lvalue.

Exceptions

  DIVISION-BY-ZERO | If the divisor expression evaluates to zero, this exception is thrown

# Xor Equals Operator (^=)

Synopsis
  Performs an exclusive-or operation on an lvalue using the value of an expression.

Syntax
  lvalue `^=` expression

Return Type
  int

Example
  $a ^= 0xf9034ba7;

Arguments Processed by ^=

Argument | Processing
All | Values are converted to integers if necessary. The expression will be evaluated and exclusive-or'ed with the lvalue, and the result will be saved to the lvalue

# Shift Left Equals Operator (<<=)

Synopsis
  Performs a shift-left operation on an lvalue using the value of an expression and returns the value assigned.

Syntax
  lvalue `<<=` expression

Return Type
  int

Example
  $a <<= 3;

Arguments Processed by <<=

Argument | Processing
All | Values are converted to integers if necessary. The expression will be evaluated and this value will determine how many bits the lvalue will be shifted left. The result will be saved to the lvalue.

# Shift Right Equals Operator (>>=)

Synopsis
  Performs a shift-right operation on an lvalue using the value of an expression and returns the value assigned.

Syntax
  lvalue `>>=` expression

Return Type
  int

Example$
  $a >>= 3;

Arguments Processed by >>=

Argument | Processing
All | Values are converted to integers if necessary. The expression will be evaluated and this value will determine how many bits the lvalue will be shifted right. The result will be saved to the lvalue.