| @c -*-texinfo-*- |
| @c This is part of the GNU Guile Reference Manual. |
| @c Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004 |
| @c Free Software Foundation, Inc. |
| @c See the file guile.texi for copying conditions. |
|
|
| @node API Overview |
| @section Overview of the Guile API |
|
|
| Guile's application programming interface (@dfn{API}) makes |
| functionality available that an application developer can use in either |
| C or Scheme programming. The interface consists of @dfn{elements} that |
| may be macros, functions or variables in C, and procedures, variables, |
| syntax or other types of object in Scheme. |
|
|
| Many elements are available to both Scheme and C, in a form that is |
| appropriate. For example, the @code{assq} Scheme procedure is also |
| available as @code{scm_assq} to C code. These elements are documented |
| only once, addressing both the Scheme and C aspects of them. |
|
|
| The Scheme name of an element is related to its C name in a regular |
| way. Also, a C function takes its parameters in a systematic way. |
|
|
| Normally, the name of a C function can be derived given its Scheme name, |
| using some simple textual transformations: |
|
|
| @itemize @bullet |
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|
| @item |
| Replace @code{-} (hyphen) with @code{_} (underscore). |
|
|
| @item |
| Replace @code{?} (question mark) with @code{_p}. |
|
|
| @item |
| Replace @code{!} (exclamation point) with @code{_x}. |
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|
| @item |
| Replace internal @code{->} with @code{_to_}. |
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|
| @item |
| Replace @code{<=} (less than or equal) with @code{_leq}. |
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|
| @item |
| Replace @code{>=} (greater than or equal) with @code{_geq}. |
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|
| @item |
| Replace @code{<} (less than) with @code{_less}. |
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|
| @item |
| Replace @code{>} (greater than) with @code{_gr}. |
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|
| @item |
| Prefix with @code{scm_}. |
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|
| @end itemize |
|
|
| @c Here is an Emacs Lisp command that prompts for a Scheme function name and |
| @c inserts the corresponding C function name into the buffer. |
|
|
| @c @example |
| @c (defun insert-scheme-to-C (name &optional use-gh) |
| @c "Transforms Scheme NAME, a string, to its C counterpart, and inserts it. |
| @c Prefix arg non-nil means use \"gh_\" prefix, otherwise use \"scm_\" prefix." |
| @c (interactive "sScheme name: \nP") |
| @c (let ((transforms '(("-" . "_") |
| @c ("?" . "_p") |
| @c ("!" . "_x") |
| @c ("->" . "_to_") |
| @c ("<=" . "_leq") |
| @c (">=" . "_geq") |
| @c ("<" . "_less") |
| @c (">" . "_gr") |
| @c ("@@" . "at")))) |
| @c (while transforms |
| @c (let ((trigger (concat "\\(.*\\)" |
| @c (regexp-quote (caar transforms)) |
| @c "\\(.*\\)")) |
| @c (sub (cdar transforms)) |
| @c (m nil)) |
| @c (while (setq m (string-match trigger name)) |
| @c (setq name (concat (match-string 1 name) |
| @c sub |
| @c (match-string 2 name))))) |
| @c (setq transforms (cdr transforms)))) |
| @c (insert (if use-gh "gh_" "scm_") name)) |
| @c @end example |
|
|
| A C function always takes a fixed number of arguments of type |
| @code{SCM}, even when the corresponding Scheme function takes a |
| variable number. |
|
|
| For some Scheme functions, some last arguments are optional; the |
| corresponding C function must always be invoked with all optional |
| arguments specified. To get the effect as if an argument has not been |
| specified, pass @code{SCM_UNDEFINED} as its value. You can not do |
| this for an argument in the middle; when one argument is |
| @code{SCM_UNDEFINED} all the ones following it must be |
| @code{SCM_UNDEFINED} as well. |
|
|
| Some Scheme functions take an arbitrary number of @emph{rest} |
| arguments; the corresponding C function must be invoked with a list of |
| all these arguments. This list is always the last argument of the C |
| function. |
|
|
| These two variants can also be combined. |
|
|
| The type of the return value of a C function that corresponds to a |
| Scheme function is always @code{SCM}. In the descriptions below, |
| types are therefore often omitted but for the return value and for the |
| arguments. |
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|
