Rebol Programming/map-each

= USAGE: = MAP-EACH 'word data body /into output

= DESCRIPTION: = Evaluates a block for each value(s) in a series and returns them as a block.

MAP-EACH is a function value. = ARGUMENTS: =
 * word -- Word or block of words to set each time (local) (Type: word block)
 * data -- The series to traverse (Type: block)
 * body -- Block to evaluate each time (Type: block)

= REFINEMENTS: =
 * /into -- Collect into a given series, rather than a new block
 * output -- The series to output to (Type: any-block any-string)

= (SPECIAL ATTRIBUTES) =
 * throw
 * catch

= SOURCE CODE = map-each: func [ {Evaluates a block for each value(s) in a series and returns them as a block.} [throw catch] 'word [word! block!] "Word or block of words to set each time (local)" data [block!] "The series to traverse" body [block!] "Block to evaluate each time" /into {Collect into a given series, rather than a new block} output [any-block! any-string!] "The series to output to" /local init len x ][ if empty? data [return any [output make block! 0]]    word: either block? word [ if empty? word [throw make error! [script invalid-arg []]] copy/deep word ] [reduce [word]] word: use word reduce [word] body: bind/copy body first word init: none parse word [any [word! | x: set-word! (               unless init [init: make block! 4]                 insert insert insert tail init first x [at data] index? x                 remove x            ) :x | x: skip (                throw make error! reduce ['script 'expect-set [word! set-word!] type? first x]            )]] len: length? word unless into [output: make block! divide length? data max 1 len] until [ set word data do init unless unset? set/any 'x do body [output: insert/only output :x] tail? data: skip data len ]    also either into [output] [head output] (        set [word data body output init x] none    ) ]