C++ Explicit type conversions Enum conversions
Example
static_cast can convert from an integer or floating point type to an enumeration type (whether scoped or unscoped), and vice versa. It can also convert between enumeration types.
- The conversion from an unscoped enumeration type to an arithmetic type is an implicit conversion; it is possible, but not necessary, to use
static_cast.
C++11
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When a scoped enumeration type is converted to an arithmetic type:
- If the enum's value can be represented exactly in the destination type, the result is that value.
- Otherwise, if the destination type is an integer type, the result is unspecified.
- Otherwise, if the destination type is a floating point type, the result is the same as that of converting to the underlying type and then to the floating point type.
Example:
enum class Format { TEXT = 0, PDF = 1000, OTHER = 2000, }; Format f = Format::PDF; int a = f; // error int b = static_cast<int>(f); // ok; b is 1000 char c = static_cast<char>(f); // unspecified, if 1000 doesn't fit into char double d = static_cast<double>(f); // d is 1000.0... probably
-
When an integer or enumeration type is converted to an enumeration type:
- If the original value is within the destination enum's range, the result is that value. Note that this value might be unequal to all enumerators.
- Otherwise, the result is unspecified (<= C++14) or undefined (>= C++17).
Example:
enum Scale { SINGLE = 1, DOUBLE = 2, QUAD = 4 }; Scale s1 = 1; // error Scale s2 = static_cast<Scale>(2); // s2 is DOUBLE Scale s3 = static_cast<Scale>(3); // s3 has value 3, and is not equal to any enumerator Scale s9 = static_cast<Scale>(9); // unspecified value in C++14; UB in C++17
C++11
-
When a floating point type is converted to an enumeration type, the result is the same as converting to the enum's underlying type and then to the enum type.
enum Direction { UP = 0, LEFT = 1, DOWN = 2, RIGHT = 3, }; Direction d = static_cast<Direction>(3.14); // d is RIGHT
