Hi,
I have the following program, which uses a switch statement to call
different template functions. The example is simple, but as the number
of shapes increase, the switch statement might be very hard to
maintain.
I'm looking for a more general solution (maybe using mpl, not sure),
such that the switch statement can be automatically generated,
therefore, more maintainable.
Thanks,
Peng
#include <iostream>
enum shape {
circle,
square // there might be many cases
};
template
struct A {
void doit() const;
};
//doit functions are defined for a majority number of shape
combinations (maybe not all, but could be defined for all---the bodies
of the functions not need can be empty).
// 3 case. There should be 4 doit's if we consider all combinations.
template <>
void A::doit() const {
std::cout << "circle circle" << std::endl;
}
template <>
void A::doit() const {
std::cout << "circle square" << std::endl;
}
template <>
void A::doit() const {
std::cout << "square circle" << std::endl;
}
void f(shape s1, shape s2) {
// each defined shape-combination corresponds to one case
// I want to generalize the code by using boost::mpl
// (or some other packages if applicable)
switch(s1 << 8 | s2) {
case circle << 8 | circle:
A().doit();
break;
case circle << 8 | square:
A().doit();
break;
case square << 8 | circle:
A().doit();
break;
default:
std::cout << "not defined" << std::endl;
}
}
int main() {
f(circle, circle);
f(circle, square);
f(square, circle);
f(square, square);
}
