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[REBOL] Re: Can I define an anti function?

From: lmecir:mbox:vol:cz at: 24-Feb-2004 17:55

Hi Romano,
>...but i agree, the :arg notation is never used and it requires a reference to a >value instead of the "value itself", so it is not totally "correct" to be used >it in context like this. > >About Scheme people, if they would speak "in general", they could be right: we >cannot create an anti :do and anti :make which work in every situations, but >if they speak only of strict bolean functions, i think they are wrong ;-) >
That's the point I was prepared to make :-) If we translate "a function returning boolean" to Rebol as a function always returning Logic! (for any input), then we are safe as you said, because DO (as well as MAKE) sometimes return different datatypes.
>... >yes, i forgot to delay the get/any insertion after the bind to the function >context. > >there are many modes to do it, and this is one of them: >
.... yes. To present a solution, that looks as simple as possible, we can write: anti: func [f [any-function!] /local exec] [ exec: func [block] reduce ['not 'apply 'first reduce [:f] 'block] func load mold third :f reduce [:exec first :f] ] , where the only missing part is an APPLY function, which takes a block of words and passes their values to the function. An easy ;-) exercise for the reader. -L