CODEWITHSUNDEEP
c++boost
stackunderflow
stackunderflow

Reputation: 907

boost::hash doesn't work for c string?

boost::hash certainly works for std::string, but does it work for c string? I've tried following code but the charHash(s2) result changes every time I run the program. It seems boost::hash takes effect on the address of s2 instead of "Hello", so the hash result varies with the random address allocated by OS.

std::string s = "Hello";
char *s2 = "Hello";
boost::hash<std::string> stringHash;
boost::hash<char *> charHash;

cout << stringHash(s) << endl; // always "758207331"
cout <<charHash(s2) << endl;   // it varies

Upvotes: 0

Views: 1354

Answers (1)

user7116
user7116

Reputation: 64068

From the documentation:

As it is compliant with TR1, it will work with:

  • integers
  • floats
  • pointers
  • strings

It also implements the extension proposed by Peter Dimov in issue 6.18 of the Library Extension Technical Report Issues List (page 63), this adds support for:

Basically, it is hashing the pointer. If you must hash a C-string, you could:

std::cout << stringHash(std::string(s2)) << std::endl;
// or the uglier...likely not equivalent
std::cout << boost::hash_range(s2, s2+strlen(s2)) << std::endl;

Upvotes: 3

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