# Coding style

## 1. Cosmetic style

C:

    indent-tabs-mode: nil
    fill-column: 79
    c-basic-offset: 4
    substatement-open: 0
    c-backslash-column: 77

Scheme:

    (put 'and-let* 'scheme-indent-function 1)
    (put 'receive 'scheme-indent-function 2)
    (put 'with-exception-handler 'scheme-indent-function 1)
    (put 'guard 'scheme-indent-function 1)

The value 77 for c-backslash-column is selected to maximize writable space, eliminate jagged end of lines and prevent overflow of lines on diffs posted to the uim-commit list.

Avoid placing a character at column 80 even if your editor displays it without overflow in 80-column window. Many editor displays it as continuance mark or folding mark. i.e. Treat column 79 as end-of-line, especially for decorations for comments.

## 2. Macro definition

Any argument should be wrapped into () or [] if no exceptional reason exist, to prevent unintended operator associations.

    #define SCM_CONS_SET_CAR(a, car)   (SCM_CAR(a) = (car))

And ultra-cowardively, passing an argument to another function or macro is should also be wrapped as follows.

    #define SCM_CONS(kar, kdr) (Scm_NewCons((kar), (kdr)))

This is intended to ensure unconditional safety against rare-cases such as follows.

    #define FOO assert(), get_foo()
    #define MAKE_LIST2(x, y) make_list(x, y)

    MAKE_LIST2(FOO, SCM_FALSE);
    /* => make_list(assert(), get_foo(), SCM_FALSE) */

## 3. Macro invocation

Don’t pass a destructive or side-effective expression to a SigScheme macro as an argument (e.g. `CONTINUATIONP(continuation_stack_unwind(cont))`), because there’s an possibility that continuation_stack_unwind() is evaluated multiple times after the macro expantion.