On Fri, 26 Mar 2010 14:25:06 +1300 Greg Ewing <greg.ewing@canterbury.ac.nz> wrote:
Eiffel's position on this seems to be that there should be no distinction -- a copy of a value should always compare equal to the original value, regardless of type.
Exactly, as I understand Eiffel. And, actually, I tend to support this point of view.
Eiffel even seems to extend this to conversions, so that if you convert an int to a float, the resulting float should compare equal to the original int, even if some precision was lost in the conversion.
Yes, there is a post-condition equivalent to "assert(newval==val)". That's why (from this point of view):
int(1.2) 1 int(1.7) 1 should not even be possible (--> exception). The programmer has to tell the language about losing information, and thus losing equality, using eg round(). [The same indeed as when converting a huge int to float.]
(Incidentally, that's one principle we would be choosing *not* to follow if we decide to compare floats and Decimals based on their exact values.)
What do you mean, exactly? There may be a reference type, then the condition is Ref(val)==Ref(newval). Or both type are referent (eg between int and float there may be loss of info in both directions). Denis ________________________________ vit esse estrany ☣ spir.wikidot.com