Constexpr if alternative

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One of pre-C++17 ways is to use partial template specializations, like here:

template <typename T, bool AorB>
struct dummy;

template <typename T, true>
struct dummy {
    static void MyFunc() {  FunctionA<T>(); }
}

template <typename T, false>
struct dummy {
    static void MyFunc() {  FunctionB<T>(); }
}

template <typename T>
void Facade() {
    dummy<T, MeetsConditions<T>::value>::MyFunc();
}

If you need more, than 2 specializations – you can use enum or integral value, and make specializations for all needed enums.

Another way is to use std::enable_if:

template <typename T>
std::enable_if<MeetsConditions<T>::value, void>::type
MyFunc() {
   FunctionA<T>();
}

template <typename T>
std::enable_if<!MeetsConditions<T>::value, void>::type
MyFunc() {
   FunctionB<T>();
}

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