This is a proposal to add further library declarations and import-set types to the large language.
Issue: Phases are not yet dealt with.
Issue: Earlier versions of this proposal included type declarations for identifiers; these have been omitted.
In R7RS it is not an error to provide a library declaration that a specific implementation does not understand, although implementations should provide warnings in such cases. Most of these declarations specified here use "should", which means that implementations are allowed to silently ignore them if they are inappropriate. Conflicts between declarations are resolved in an implementation-specific way. Exceptions:
(reexport import-set ...)
Like import, but also exports all identifiers that were imported. This allows a library to easily extend one or more other libraries.
(export-all identifier ...)
Exports all defined identifiers except for identifiers, if any. Imported identifiers are not re-exported.. This allows a library to be easily extended.
In the list below, importance represents a symbol, one of unimportant (no importance), neutral (some importance, the default), important (substantial importance), or extreme (extreme importance). It is an error to specify anything else. These correspond to the Common Lisp importance values 0, 1, 2, and 3 respectively.
If no identifiers are named, then the library declaration applies to all identifiers defined in the library. Implementations may (but should not) ignore the named identifiers and treat the declaration as applying to all identifiers.
(speed importance identifier ...)
The named identifiers should be processed so as to maximize execution speed to the extent specified by importance.
(space importance identifier ...)
The named identifiers should be processed so as to minimize the use of space at run time to the extent specified by importance.
(safety importance identifier ...)
The named identifiers should be processed so as to maximize safety at execution time to the extent specified by importance.
(compilation-speed importance identifier ...)
The named identifiers should be processed so as to maximize compilation speed to the extent specified by importance.
(debuggability importance identifier ...)
The named identifiers should be processed so as to maximize ease of debugging to the extent specified by importance.
(library-error literal-string)
Signals an error when the library is first examined. It is meant to be used within cond-expand library declarations to trigger an error if some feature or library is found not to be present. Applications cannot count on being able to catch this error with exception handlers or guards.
If no identifiers are named, then the library declaration applies to all identifiers defined in the library. Implementations may (but should not) ignore the named identifiers and treat the declaration as applying to all identifiers.
(inline identifier ...)
The procedures named by the identifiers should be inlined by the compiler, if there is one.
(notinline identifier ...)
The procedures named by the identifiers must not be inlined by the compiler, if there is one.
(unused identifier ...)
The implementation should not warn the user if the identifiers are defined but not used in the library.
(report [verbose|terse|silent] identifier ...)
The implementation should process the definitions of the named identifiers verbosely, tersely, or silently. Even in silent mode, however, the user should still be notified of errors.
If no identifiers are named, then the library declaration applies to all identifiers defined in the library. Implementations may (but should not) ignore the named identifiers and treat the declaration as applying to all identifiers.
(no-location identifier ...)
The implementation may assume that the procedures bound to identifier have no location, so that neither eq? nor eqv? is required to return #t in any circumstances when passed a such a procedure as an argument.
To allow library declarations in main programs (not in files of code included by include or include-ci), the following new syntax is added:
(specify-declarations declaration ...)
Allows any library declaration except export and reexport to be included as part of a main program. It is an error for declare to appear except at the beginning of a main program. For backward compatibility with R7RS-small, programmers should avoid wrapping import, include, include-ci, or begin declarations in specify-declarations.
The more natural term declare is avoided because some implementations use it for related but implementation-specific uses.
(drop-prefix import-set identifier)
Import sets of this kind automatically renames identifiers in the given import-set: any of them which begin with the characters in identifier have those characters removed.
For example, if the library (foo) exports identifiers foo-a, foo-b, and foo-c, then (import (drop-prefix (foo) foo-) will import them under the names of a, b, and c respectively. (Chibi Scheme already supports this type of import set.)
(provide feature ...)
As a consequence of loading this library, the specified features are made immediately available to future cond-expand library declarations, to cond-expand syntax, and to the features procedure.
See also InterfacesCowan.