[boost] [String algorithm] is_any_of has inefficient implementation

From: Joe Gottman (jgottman_at_[hidden])
Date: 2008-02-13 20:43:40

I just discovered that the string algorithm predicate is_any_of has an 
inefficient implementation. Internally it uses a std::set.  There are 
two problems with this.  First, since the order of the characters does 
not matter, std::unordered_set is probably faster.  Second, the 
contained set has to be copied each time the object is used in, for 
instance, a split() statement.  Since split can reuse a predicate 
literally thousands of times when splitting a large string, this is a 
lot of unnecessary copying.

Joe Gottman