Andy Little ha scritto:
BTW An alternate signature for the function:
template <typename T> struct compare_absolute_error /*not derived from binary_function!*/ { T eps; compare_absolute_error(T eps_) : eps(eps_) {}
//Signature as thus to prevent too many conversions template <typename T1, typename T2> bool operator()(T1 const & x, T2 const & y) const { return abs(x - y) < eps; } };
// ............. possible useage :
compare_absolute_error<int> comp(1);
int pixel_x =100; float current_pos_x = 100.5;
bool grabbed = comp(current_pos_x, pixel_x);
The idea is nice, but in this particular case I think the "fixed" version is more suitable. First: the user can be sure about what approximation is going to be used for the comparison (in the realm of floating point, it's a big help). Second: knowing the type in advance allows you to deal correctly with corner cases (infinities, denorm, etc.). With the member-template approach that you suggest you would have to handle more cases and it might easily get tedious. Ganesh