Understanding the need for concepts
As briefly mentioned in the introduction to this chapter, there are some important benefits that concepts provide. Arguably, the most important ones are code readability and better error messages. Before we look at how to use concepts, let’s revisit an example we saw previously and see how it stands in relation to these two programming aspects:
template <typename T>
T add(T const a, T const b)
{
return a + b;
}
This simple function template takes two arguments and returns their sum. In fact, it does not return the sum, but the result of applying the plus operator to the two arguments. A user-defined type can overload this operator and perform some particular operation. The term sum only makes sense when we discuss mathematical types, such as integral types, floating-point types, the std::complex type, matrix types, vector types, etc.
For a string type, for instance, the plus operator can mean concatenation...
