operator _opt.md

operator""_opt()

User-defined literal operators for constructing a KwargsKeyLiteral (an adapter for KwargsKey). Several overloads are provided:

---

constexpr KwargsKeyLiteral operator""_opt(const char* const __str, std::size_t __size) noexcept;

Matches string literals.

Examples:

• "data"_opt
• "123"_opt
• ""_opt

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template<char... _String>
constexpr KwargsKeyLiteral operator""_opt() noexcept;

Matches integer and floating-point literals.

Examples:

• 123_opt
• 0_opt
• 20.02_opt
• 999999999999999999999999999999999_opt
• 9999999999999999.9999999999999999999_opt

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constexpr KwargsKeyLiteral operator""_opt(char __ch) noexcept;

Matches character literals.

Examples:

• 'a'_opt
• 'A'_opt
• '\n'_opt