Genetic.h:19: error: expected ‘,’ or ‘...’ before ‘>’ token

Genetic.h:19: error: wrong number of template arguments (1, should be 2)
/usr/lib/gcc/i486-linux-gnu/4.1.2/../../../../include/c++/4.1.2/bits/stl_pair.h:68: error: provided for ‘template<class _T1, class _T2> struct std::pair’

Genetic.h:19: error: default argument missing for parameter 4 of ‘GeneNode::GeneNode(GeneNode*, GeneNode*, std::pair<char, int>, int)’

make: *** [Genetic.o] Error 1



line 19:
GeneNode(GeneNode* l = NULL, GeneNode* r = NULL, pair<char, int> ch = pair<char, int> (0,0)) : left (l), right(r), data(ch) {}