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Source for wiki CombinatorsCowan version 7
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cowan
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ipnr
127.10.177.1
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CombinatorsCowan
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0
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This proposal contains various procedures that return procedures and a few others, drawn from Chicken. Common Lisp has a few of them too.
== Combinators ==
`(constantly `''obj'' ...`)`
Returns a procedure that always returns the ''obj'' objects as its values, regardless of the number and value of its arguments.
`(complement `''proc''`)`
Returns a procedure that returns the boolean inverse of ''proc''. That is, it returns `#t` when ''proc'' returns `#f`, and `#f` otherwise.
`(compose `''proc'' ... `)`
Returns a procedure that represents the composition of its arguments. Any of the procedures may return multiple values, which are passed as arguments to its successor. With zero arguments, `(compose)` returns a procedure that is functionally equivalent to `values`.
`(simple-compose `''proc'' ...`)`
A variant of `compose` that handles only single-argument single-valued procedures. With zero arguments, returns a procedure that is functionally equivalent to `identity`.
`(conjoin `''predicate'' ...`)`
Returns a procedure that returns `#t` if its argument satisfies all the ''predicate''s.
`(disjoin `''predicate'' ...`)`
Returns a procedure that returns `#t` if its argument satisfies any of the ''predicate''s.
`(each `''proc'' ... `)`
Returns a procedure that applies each of the ''proc''s in turn to its arguments, discarding the results and returning an unspecified value.
`(flip `''proc''`)`
Returns a two-argument procedure that calls ''proc'', a two-argument procedure, with its arguments swapped.
`(all-of? `''predicate''`)`
Returns a procedure of one argument that returns `#t` when applied to a list of elements that all satisfy ''predicate'', or `#f` otherwise.
`(any-of? `''predicate''`)`
Returns a procedure of one argument that returns `#t` when applied to a list of elements at least one of which satisfies ''predicate'', or `#f` otherwise.
`(map-reduce `''mapper reducer''`)`
Returns a procedure that applies ''mapper'' to each of its arguments, and then applies ''reducer'' to all the results and returns what it returns.
== Other procedures ==
`(always `''obj''`)`
Ignores its arguments and always returns `#t`.
`(never `''obj''`)`
Ignores its arguments and always returns `#f`.
`(identity `''obj''`)`
Returns ''obj''.
== Documentation style ==
It's been suggested that the documentation of these combinators is too hard to understand, and should be documented
like this:
`((constantly `''obj'' ...`) `''arg'' ...`)`
Ignores ''args'' and returns ''objs''.
time
2013-06-03 22:56:38
version
7