Return a variant of BS, a build system, that uses TOOLCHAIN instead of the default GNU C/C++ toolchain. TOOLCHAIN must be a list of inputs (label/package tuples) providing equivalent functionality, such as the 'gcc-toolchain' package.

Ask BUILD-SYSTEM to return a 'bag' for NAME, with the given SOURCE, INPUTS, NATIVE-INPUTS, OUTPUTS, and additional ARGUMENTS. If TARGET is not #f, it must be a string with the GNU triplet of a cross-compilation target.

This is the mechanism by which a package is "lowered" to a bag, which is the intermediate representation just above derivations.

Return a fixed-output derivation that fetches REF, a <bzr-reference> object. The output is expected to have recursive hash HASH of type HASH-ALGO (a symbol). Use NAME as the file name, or a generic name if #f.

Return #t if DATE is obsolete compared to NOW + TTL seconds.

Return a procedure that, when passed a file, returns its "expiration time" computed as its timestamp + TTL seconds. Call TIMESTAMP to obtain the relevant timestamp from the result of 'stat'.

Like 'delete-file', but does not raise an error when FILE does not exist.

Given ENTRIES, a list of file names, remove those whose expiration time, as returned by ENTRY-EXPIRATION, has passed. Use DELETE-ENTRY to delete them.