[REBOL] APL'ish operations Re:(2)
From: rohitjain1:yaho:o at: 25-Jul-2000 6:04
--- [bhandley--zip--com--au] wrote:
> There are two ways you could go, depending on what
> you want.
> Change each element within the series, or return a
> new series with the
> result of your operation applied to each element.
>
> For the first approach...
>
> values-block: [1 2 3]
> while [not tail? values-block] [
> values-block: change values-block values-block/1
> * 7
> ]
> values-block: head values-block ; Sets the series
> back to it's head.
> print values-block
This is what I tried. Doesn't work...
> For the second approach....
>
> >> source-block: [1 2 3]
> == [1 2 3]
> >> result-block: make block! 3
> == []
> >> foreach elt source-block [
> [ append result-block elt * 7
> [ ]
> == [7 14 21]
> >> print result-block
> 7 14 21
>
This works! Thanks..
> For something more advanced...
>
> With due credit to the original authors Ladislav
> Mecir and Carl Sassenrath.
> Below is a function that does it. This function is
> advanced in the sense
> that it takes a function as an argument. Passing the
> function in is done in
> a special way.
>
> map: func [{Maps a function to all elements of a
> block}
> f [any-function!] blk [block!]
> /local result
> ][
> result: make block! length? blk
> foreach elem blk [
> append/only result f :elem
> ]
> result
> ]
>
> Use it like this:
> >> my-func: func[x][ x * 7] ; Here I declare my
> function. my-func is a
> word that refers to the created function.
> >> map :my-func [1 2 3] ; Here I call map, the
> colon gets the value of
> my-func word - in this case the function I created.
> == [7 14 21]
> >>
Perfect. Just what I needed. Wish there was a way to
make simple one-off functions in a block like [ + 5]
etc.
