You see K. Beck in his book smalltalk best pratices promotes this form. So can you propose a better solution so that we learn? Stef Le 11/1/16 10:09, David Allouche a écrit :
Since it's not obvious why xor-ing is a bad way to produce hash, here is a link that gives some background
https://en.wikipedia.org/wiki/Hash_function#Uniformity
On 11 Jan 2016, at 10:01, David Allouche <david@allouche.net> wrote:
I happened to look at the new code for LayoutFrame>>#hash
hash ^self species hash bitXor: (self leftFraction bitXor: (self leftOffset bitXor: (self topFraction bitXor: (self topOffset bitXor: (self rightFraction bitXor: (self rightOffset bitXor: (self bottomFraction bitXor: self bottomOffset)))))))
This is a terrible, terrible way to compute a hash.
0 xor 0 = 1 xor 1 = 2 xor 2 = etc.
NEVER compute hashes with xor, that's wrong, and it causes horrible, hard to debug, performance bugs down the road.
SequenceableCollection>>#hash looks more like a correct way of doing it. I do not know what is the correct, efficient way to reuse this logic in LayoutFrame>>#hash.
By the way, how do you guys do code reviews for code integrated into the core?