On Apr 26, 4:42 pm, Adam Skutt <ask...@gmail.com> wrote: > > In a mathematical sense, you're saying that given f(x) = x+2, using > f(x) is somehow more "direct" (whatever the hell that even means) than > using 'x+2'. That's just not true. We freely and openly interchange > them all the time doing mathematics. Programming is no different.
If f(x) and x+2 are freely interchangeable then you have referential transparency, a property that only purely functional languages have. In python: >>> a = [1,2] >>> m1 = [a, a] >>> m2 = [[1,2],[1,2]] may make m1 and m2 seem like the same until you assign to m1[0][0]. eg One would not be able to distinguish m1 and m2 in Haskell. On the whole I whole-heartedly agree that 'a is b' be replaced by id(a) == id(b), with id itself replaced by something more obviously implementational like addrof. The reasons are fundamental: The word 'is' is arguably the primal existential verb. Whereas 'is' in python is merely a leakage of implementation up to the programmer level: http://www.joelonsoftware.com/articles/LeakyAbstractions.html Such a leakage may be justified just as C allowing inline asm may be justified. However dignifying such a leakage with the primal existential verb causes all the confusions seen on this thread (and the various stackoverflow questions etc). -- http://mail.python.org/mailman/listinfo/python-list
