Types of Constraints

1. Conjunctions

It combines multiple constraints using AND (&) operator. It specifies that all the constraints within the conjunction must be satisfied for the overall constraint to be satisfied.

template <typename T>
requires Constraint1 && Constraint2 && ... && ConstraintN
void functionName(T parameter) {
   // Function body
}

2. Disjunctions

It is used to combine multiple constraints with the help of the OR (||) operator. It specifies that at least one of the constraints within the disjunction must be satisfied for the overall constraint to be satisfied.

template <typename T>
requires Constraint1 || Constraint2 || ... || ConstraintN
void functionName(T parameter) {
   // Function body
}

3. Atomic constraints

They are individual constraints that define specific requirements on types, expressions, or template arguments.

template <typename T>
concept ConceptName = Constraint1 && Constraint2 && ... && ConstraintN;

template <typename T>
requires ConceptName<T>
void functionName(T parameter) {
   // Function body
}

In this article, we will learn about the constraints and concepts with the help of examples in a simple way. So, it is a feature that was introduced in the latest version i.e. C++20 that specifies requirements on template arguments and enables more expressive and readable code.