Il giorno 18/mag/2015, alle ore 20.50, Jos Koot ha scritto: > I think Rackets's reference and guide are *very clear* about eq?, eqv? and > equal?.
Yes, right. It was the Racket Reference to tell me exactly that eqv? is an eq? that works for numbers and characters, too. I really had to look this up and found an simple and concise description. But the entries for for-each and map do not state anything about the execution order of the list processing. The other entry whose description I found a bit confusing was "cond" - I always need to look that up no matter which Scheme I'm on because I always (want to) forget that it takes only the first branch whose condition is true and ignores the rest. Perhaps someday they will change this but R5RS states that behavior clearly enough. That's what I meant when I wrote "the guide and the reference are sometimes a bit vague about these things" and I'm sorry about being too vague about it. > They are even described well for structures and hashes and much more. > Be aware, though, that in general equality can be interpreted in many ways. > At the mathematical level equality is a difficult and in many cases even an > unsolvable thing. Maybe, I never thought about that in mathematical terms if not with the concept of identity. How could they do without it? Two objects (in memory) are identical when ... no, they preferred talking about sameness. Perhaps they were right; for each and every case you can define equality rather well. But equality as an abstract concept may lead to a search in nothing which can take forever and ever: like the moon that keeps circling around the earth without any reason one's mind can circle around nothing. That's mighty. But that's off topic. -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
