Why Should I Avoid Using `std::enable_if` in Function Signatures?

Why Should I Avoid std::enable_if in Function Signatures?

Avoiding std::enable_if in Function Parameters

Using std::enable_if in function parameters introduces complexity and can make code difficult to read. It also complicates template argument deduction and can lead to unexpected behavior.

Solution: Define overloaded functions for each desired behavior, using sfinae to select the appropriate function.

std::enable_if as Template Parameter

Preferring std::enable_if as a template parameter provides several advantages:

• Readability: Keeps enable_if use and return/argument types separate, simplifying code understanding.
• Universal Applicability: Works for all template structures, including constructors and operators without return types or extra arguments.

std::enable_if as Return Type

While using std::enable_if as a return type is technically possible, it's not ideal due to the following:

• It's not part of the normal function signature, making it harder to identify the intended behavior.
• It can introduce subtle errors when using templates with multiple types of arguments.

Differences for Member and Non-Member Function Templates

The same principles apply to both member and non-member function templates. However, member function templates may have additional considerations, such as the accessibility of private or protected members.

Recommendation

Follow the guideline of "Put the hack in the template parameters." By placing std::enable_if on template parameters, you enhance readability, ensure universal applicability, and simplify template argument deduction.

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