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Source for wiki CombinatorsCowan version 12

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cowan

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127.11.51.1

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CombinatorsCowan

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This proposal contains various procedures that return procedures as well as a few others, drawn from an earlier version of Chicken.  Common Lisp has a few of them too.


== Combinators ==

The documentation style, rather than showing only how the procedures are invoked, also shows how the returned procedures would be invoked.  This is done in order to make the descriptions easier to understand.

`((constantly `''obj'' ...`)` ''arg'' ...`)`

Returns the ''obj'' objects as its values, ignoring ''args''.

`((complement `''proc''`)` ''obj''`)`

Returns `#t` when `(''proc obj''`)` returns `#f`, and `#f` otherwise.

`((compose `''proc'' ... `)` ''arg'' ...`)`

Passes the ''args'' to the first ''proc'', which returns any number of values.  These are then passed to the next ''proc'', and so on until the final ''proc'' is reached.  If there are no ''procs'', returns its arguments as values.

`((simple-compose `''proc'' ...`)` ''arg''`)`

Passes ''arg'' to the first ''proc'', which returns one value.  This is then passed to the next ''proc'', and so on until the final ''proc'' is reached.  If there are no ''procs'', returns its argument.

`((conjoin `''predicate'' ...`)` ''arg'' ...`)`

Returns `#t` if the ''args'' satisfy all the ''predicates'', and `#f` otherwise.

`((disjoin `''predicate'' ...`)` ''arg'' ...`)`

Returns `#t` if the ''args'' satisfy any of the ''predicate''s.

`((each `''proc'' ... `)` ''arg'' ...`)`

Applies each of the ''proc''s in turn to ''args'', discarding the results and returning an unspecified value.

`((flip `''proc''`)` ''arg1 arg2''`)`

Returns `(`''proc arg2 arg1''`)`.

`((all-of? `''predicate''`)`

Applies ''predicate'' to each element of ''list'' in turn, and immediately returns `#f` if ''predicate'' is not satisfied by that element; otherwise returns `#t`.

`((any-of? `''predicate''`)` ''list''`)`

Applies ''predicate'' to each element of ''list'' in turn, and immediately returns `#t` if ''predicate'' is satisfied by that element; otherwise returns `#f`.

`((map-reduce `''mapper reducer''`)` ''list''`)`

Returns ``(apply ''reducer'' `(`''mapper list''`))`.

== Other procedures ==

`(always `''obj''`)`

Ignores its arguments and always returns `#t`. 

`(never `''obj''`)`

Ignores its arguments and always returns `#f`.

`(identity `''obj''`)`

Returns ''obj''.

time

2014-12-12 12:16:51