Pack canny_tudor -- prolog/swi/compounds.pl

flatten_slashes(+Components0:compound, ?Components:compound) is semidet

Flattens slash-delimited components. Components0 unifies flatly with Components using mode(+, ?). Fails if Components do not match the incoming Components0 correctly with the same number of slashes.

Consecutive slash-delimited compound terms decompose in Prolog as nested slash-functors. Compound a/b/c decomposes to /(a/b, c) for example. Sub-term a/b decomposes to nested /(a, b). The predicate converts any /(a, b/c) to /(a/b, c) so that the shorthand flattens from a/(b/c) to a/b/c.

Note that Prolog variables match partially-bound compounds; A matches A/(B/C). The first argument must therefore be fully ground in order to avoid infinite recursion.

To be done: - Enhance the predicate modes to allow variable components such as A/B/C; mode (?, ?).

append_path(?Left, ?Right, ?LeftAndRight) is semidet

LeftAndRight appends Left path to Right path. Paths in this context amount to any slash-separated terms, including atoms and compounds. Paths can include variables. Use this predicate to split or join arbitrary paths. The solutions associate to the left by preference and collate at Left, even though the slash operator associates to the right. Hence append_path(A, B/5, 1/2/3/4/5) gives one solution of A = 1/2/3 and B = 4.

There is an implementation subtlety. Only find the Right hand key if the argument is really a compound, not just unifies with a slash compound since Path/Component unifies with any unbound variable.