Dr. J. J. "One Eyed CrackerJack" Harbaugh -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Anton Rolls Sent: Friday, November 21, 2003 1:09 AM To: [EMAIL PROTECTED] Subject: [REBOL] Re: Apparent newbie question Rebol is strict about left to right evaluation. I remember Holger commenting about in-fix operators (operators with two surrounding arguments) that when you see an expression like this: 1 > 2 then you need to imagine that the ">" moves to the front: > 1 2 (to be a prefix operator.) Now it looks like any other function. So in the expression: length? test-block < 4 you should imagine this: length? < test-block 4 Now rebol will evaluate like this: length? (< test-block 4) which leads to the error: ** Script Error: Expected one of: block! - not: integer! Who expected it? The < operator, of course. Anton. > Hi Steven, > > As you've seen from all the answers so far, precedence matters with > operators. The Core guide says (in the Math section) that there are > just two > rules: > > Expressions are evaluated from left to right. > Operators take precedence over functions. > > For a long time while I was learning REBOL I basically ignored > operators like +, -, * etc. Instead I used their function equivalents: > Add, Subtract, Multiply. Once I got comfortable with the precedence > rules of operators I started using a mix. Eg. > > Add 3 * X 4 * Y > > instead of > > (3 * X) + (4 * Y) > > Every now and then I get the precedence stuff mixed up and instead of > inserting heaps of paren! I revert to using the function style. > > Most recently, after Joel's post on coding habits and the effect > of changing > them, I've started using a different habit for If conditions more akin to > the other posts. > > if x = 4 * Y [...] > > Regards, > Brett. -- To unsubscribe from this list, just send an email to [EMAIL PROTECTED] with unsubscribe as the subject. -- To unsubscribe from this list, just send an email to [EMAIL PROTECTED] with unsubscribe as the subject.
