srfi.7 - Feature-based program configuration language ¶This module provides a program configuration metalanguage
(program form) defined in srfi-7.
Gauche autoloads srfi.7 module, so you don’t need
to say (use srfi.7) explicitly.
Note that the program form isn’t necessary to be a
Scheme expression. SRFI-7 allows an implementation to preprocess
the program form to produce a Scheme program, then
executes it with different means.
Gauche implements program form as a macro, so it can
evaluates the form directly. Nonetheless, it doesn’t make sense
to mix program form and other forms in one file,
or expecting a return value of program form.
A typical usage of program form is to prepare a single
file which just contains program form. (It can load
other files using files clause (see below) within the
program form.) To execute such a program file in Gauche,
you can just load it.
[SRFI-7]{srfi.7}
This is a configuration language to structure a Scheme program,
based on availability of the features.
A Scheme program is constructed from the program form.
Gauche evaluates the constructed Scheme program on-the-fly.
Each program-clause needs to be one of the "Program Clauses" below.
[SRFI-7] The feature-id’s are the same as SRFI-0’s (see Feature conditional). It tells that the following code requires these feature-id’s.
If a feature-id which is not supported in Gauche is given, an error is signaled.
[SRFI-7] Inserts the content of the filenames into a program. In Gauche, this clause just causes filenames to be loaded into the current module.
[SRFI-7] The scheme-expressions are inserted into a program.
[SRFI-7] Clause is a following form:
(requirement program-clause program-clause2 ...)
Where requirement should be one of the following:
(and requirement …)
(or requirement …)
(not requirement)
The requirement of the last clause may be else.
Gauche checks each requirement one by one, and if it finds a fulfilled requirement, inserts the program-clauses in that clause into the program.