R6RS Version References (Guile Reference Manual)

Warning: This is the manual of the legacy Guile 2.2 series. You may want to read the manual of the current stable series instead.

6.20.5 R6RS Version References

Guile’s module system includes support for locating modules based on a declared version specifier of the same form as the one described in R6RS (see R6RS Library Form in The Revised^6 Report on the Algorithmic Language Scheme). By using the #:version keyword in a define-module form, a module may specify a version as a list of zero or more exact, nonnegative integers.

This version can then be used to locate the module during the module search process. Client modules and callers of the use-modules function may specify constraints on the versions of target modules by providing a version reference, which has one of the following forms:

 (sub-version-reference ...)
 (and version-reference ...)
 (or version-reference ...)
 (not version-reference)

in which sub-version-reference is in turn one of:

 (sub-version)
 (>= sub-version)
 (<= sub-version)
 (and sub-version-reference ...)
 (or sub-version-reference ...)
 (not sub-version-reference)

in which sub-version is an exact, nonnegative integer as above. A version reference matches a declared module version if each element of the version reference matches a corresponding element of the module version, according to the following rules:

The and sub-form matches a version or version element if every element in the tail of the sub-form matches the specified version or version element.
The or sub-form matches a version or version element if any element in the tail of the sub-form matches the specified version or version element.
The not sub-form matches a version or version element if the tail of the sub-form does not match the version or version element.
The >= sub-form matches a version element if the element is greater than or equal to the sub-version in the tail of the sub-form.
The <= sub-form matches a version element if the version is less than or equal to the sub-version in the tail of the sub-form.
A sub-version matches a version element if one is eqv? to the other.

For example, a module declared as:

 (define-module (mylib mymodule) #:version (1 2 0))

would be successfully loaded by any of the following use-modules expressions:

 (use-modules ((mylib mymodule) #:version (1 2 (>= 0))))
 (use-modules ((mylib mymodule) #:version (or (1 2 0) (1 2 1))))
 (use-modules ((mylib mymodule) #:version ((and (>= 1) (not 2)) 2 0)))