C++ SFINAE and Concepts | Template Constraints from C++11 to C++20
이 글의 핵심
Bridge SFINAE-based constraints and C++20 concepts: when substitution fails silently, and how `requires` makes intent explicit.
What is SFINAE?
Substitution Failure Is Not An Error—if substituting template arguments into a signature fails, that overload is discarded rather than necessarily causing an error, as long as another viable candidate exists.
enable_if
Classic pattern to enable declarations only when std::is_* predicates hold—prefer enable_if_t in modern code.
type_traits
is_integral, remove_const, is_same, etc.—building blocks for both SFINAE and concepts.
Concepts (C++20)
#include <concepts>
template<typename T>
concept Numeric = std::integral<T> || std::floating_point<T>;
template<Numeric T>
T add(T a, T b) {
return a + b;
}requires expressions
Express syntactic and semantic requirements on types; compiler checks them at template definition/use sites.
Practical examples
The Korean article includes: container detection SFINAE vs Container concept, callable detection, arithmetic average, Comparable clamp, composite concepts, and improved error messages with concepts.
SFINAE vs concepts
Concepts usually read better and fail with clearer diagnostics—still learn SFINAE for legacy code and library techniques.
Common pitfalls
SFINAE failures when signatures are malformed, circular concept definitions, overly strict ad-hoc concepts.
FAQ
Prefer concepts in new C++20 code; keep SFINAE tools for interoperability and understanding the standard library.
Related posts
- Type traits
- Metaprogramming evolution
- SFINAE
Keywords
C++, SFINAE, Concepts, templates, metaprogramming.
See also
- Metaprogramming evolution
- Advanced metaprogramming
- Type traits
enable_if- Expression templates