AMDG On 03/25/2011 06:57 AM, Michael Goldshteyn wrote:
After reading the explanation of how hash_combine should be used, I am left wondering. Why is the recommendation for hash_combine different from what one would intuitively expect?
Either one is okay.
Namely, given:
struct MyStruct { int a; int b; int c; };
The recommendation via examples and documentation is:
size_t hash(const MyStruct &s) { size_t hashValue=0;
// Combine hashes of all elements hash_combine(hashValue,s.a); hash_combine(hashValue,s.b); hash_combine(hashValue,s.c);
return hashValue; }
Rather than what I would think is the expected correct approach:
size_t hash(const MyStruct &s) { // For a composite hash, start by hashing the first element size_t hashValue=hash_value(s.a);
// Then, combine with hashes of the remaining elements hash_combine(hashValue,s.b); hash_combine(hashValue,s.c);
return hashValue; }
In Christ, Steven Watanabe