Picking the Right Standard Concept

What this C++ template constraint question tests

This is an easy C++ question that probes your familiarity with modern standard library concepts and how to express type requirements precisely. It reflects the kind of constraint reasoning that matters when writing generic code that accepts some types but explicitly rejects others.

The question focuses on selecting the right standard concept to narrow a template's applicability. Rather than writing custom type-checking logic, the goal is to recognize which existing concept from the C++ standard library captures the exact semantic requirement: permitting numeric types while blocking incompatible ones like strings. This skill is essential when designing APIs that are both flexible and type-safe.

• C++20 concepts and their semantics
• Numeric vs. non-numeric type categories
• Standard library concept predicates