[REBOL] Re: 'do vs 'reduce
From: nitsch-lists::netcologne::de at: 6-Jan-2004 5:24
Am Montag 05 Januar 2004 17:59 schrieb Gregg Irwin:
> Hi Andreas,
>
> AB> i was wondering if, letting refinements and non-block! parameters
> AB> aside, 'do is really just a "last reduce", in other words, if (a
> AB> simplified) do could be precisely expressed as:
>
> AB> do: func [ bl [block!] ] [ last reduce bl ]
>
> Well, both cause evaluation. If LOAD were used (thinking about binding
> issues), and having not done any tests, my feeling is that you're
> probably right. Knowing how Carl likes to build things, I can't
> imagine he'd want two separate evaluators in REBOL. :)
>
similar, but
1) [do %file.r] <> [reducce %file.r]
2) 'do can give arguments to expressions. the only function with a dynamic
number of arguments:
!>> reduce func[a][a * a] 5
== 5 ; reduce-result is thrown away
!>> do func[a][a * a] 5
== 25 ; 5 is past to func by do. 'do fetches actually 2 arguments in this
case.
!>> do pick a-block-with-funcs 5 ; would work too
3) does not create a block, should be faster.
> -- Gregg
-Volker
