Home » Tip Bank » C++

Language: C++
Expertise: Intermediate

Jul 13, 2004

Often, in code, you find yourself constraining values doing something like:

if(val < MIN)
  val = MIN;
else if(val > MAX)
  val = MAX;

This simple template function will do that for you. The template uses two types, so that the in value doesn't have to be the same type as the constraints. As long as a comparison operator is defined between them, it will still work.

template<class T, class U>
T clamp(T in, U low, U high)
{
    if(in <= low)
        return low;
    else if(in >= high)
        return high;
    else
        return in;
}

If you are trying to restrain a value in just one direction, it is easiest to use std::min(a,b) and std::max(a,b).

Usage:

double degrees;
cin >> degrees;
degrees = clamp(degrees,0,360);     
//restrain degrees to an appropriate value

val = std::max(val,0);     
//make sure value doesn't drop below 0

people_to_invite = std::min(people_not_invited,seats_left);  
//ensure value doesn't get above seats_left