[REBOL] Re: Evaluating if's
From: gscottjones::mchsi::com at: 2-Jul-2002 4:42
From: "Charles"
> Here's a little question. Perhaps I've been
> spoiled in other languages, but this is starting
> to frustrate me. I have something like:
> if THIS and THAT []
> Thing is, if THIS is false, it continues to
> evaluate THAT anyways. What's the point?
> The result is obviously false anyways. I'm
> working on a case like this (perhaps
> someone can provide a more elegant solution):
> if (2 = length? p: parse filename ".") AND (not none? find pick p 2
htm
)
> [ ...
> Obviously, if the first condition is false,
> I want it to quit without evaluating the second
> condition. Help? Any way I can continue doing
> this in the same line, and without worrying about
> throwing and catching errors? Or am I more or
> less doomed to yet another nested if? Thanks folks.
Hi, Charles,
Two helpful words are 'any and 'all. An ad hoc session at a *fresh* console
demonstrates that 'all short cuts if false:
if all [1 > 2 c: 3 = 3] [ print "hello"] ;== none
probe c ;;;;;value of c was not set
;** Script Error: c has no value
;** Where: connect-to-link
;** Near: probe c
if all [1 < 2 c: 3 = 3] [ print "hello"] ;hello
probe c ;== true
Hope that this both helps and causes REBOL to also spoil you.
:-)
--Scott Jones
