C++ named requirements: BitmaskType
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Defines a type that can be used to represent a set of constant values or any combination of those values. This trait is typically implemented by integer types, std::bitset, or enumerations (scoped and unscoped) with additional operator overloads.
[edit] Requirements
The bitmask type supports a finite number of bitmask elements, which are distinct non-zero values of the bitmask type, such that, for any pair Ci and Cj, Ci & Ci is nonzero and Ci & Cj is zero. In addition, the value 0 is used to represent an empty bitmask, with no values set.
The bitwise operators operator&, operator|, operator^, operator~, operator&=, operator|=, and operator^= are defined for values of the bitmask type and have the same semantics as the corresponding built-in operators on unsigned integers would have if the bitmask elements were the distinct integer powers of two.
The following expressions are well-formed and have the following meaning for any BitmaskType:
| Expression | Meaning |
| X |= Y | sets the value Y in the object X
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| X &= ~Y | clears the value Y in the object X
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| X & Y | nonzero result indicates that the value Y is set in the object X
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Each representable bitmask element is defined as an inline(since C++17) constexpr value of the bitmask type.
[edit] Standard library
The following standard library types satisfy BitmaskType:
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Code that relies on some particular implementation option (e.g. int n = std::ios_base::hex) is non-portable because std::ios_base::fmtflags is not necessarily implicitly convertible to int.
