stlab-enum-ops

Description

enum_ops provides optional typesafe bitset and arithmetic operations for enumeration types. Without these typesafe operations, the compiler will promote the operand(s) to the appropriate integral type, and the result will be an integral type. When the typesafe operations have been defined for an enumeration type, E, the result will be of type E exactly when the operand(s) are of type E.

Available Operations

Customization Points

Functions to enable typesafe operations for enum types.

These functions must be overloaded in your enum's namespace to enable the corresponding operations for your enum type.

• View all customization functions

Bitmask Operations

Bitwise operations for bitmask-enabled enums.

These operations are available when you enable bitmask operations by defining:

auto stlab_enable_bitmask_enum(YourEnum) -> std::true_type;

• View all bitmask operations

Arithmetic Operations

Arithmetic operations for arithmetic-enabled enums.

These operations are available when you enable arithmetic operations by defining:

auto stlab_enable_arithmetic_enum(YourEnum) -> std::true_type;

• View all arithmetic operations

Common Operations

Operations available for both bitmask and arithmetic-enabled enums.

These operations are available for enums that have either bitmask or arithmetic operations enabled.

• View all common operations

Definition

Defined in stlab/enum_ops.hpp

Example

The following is an example of code that will compile:

#include <stlab/enum_ops.hpp> 
 
#include <iostream>
 
enum foo { foo_4 = 1 << 2, foo_8 = 1 << 3 };
enum class views : int { none = 0, text = 1 << 0, icon = 1 << 1, preview = 1 << 2 };
 
auto stlab_enable_bitmask_enum(foo) -> std::true_type;
auto stlab_enable_bitmask_enum(views) -> std::true_type; 

int main() {
    // Bitset operations on plain enums
    foo a{foo_4};
    foo b{foo_8};
    foo c{a | b};
    std::cout << a << " " << b << " " << c << "\n";
 
    // Bitset operations on enum class
    views x = views::text | views::icon;
    bool has_text = (x & views::text) == views::text;
    bool has_preview = (x & views::preview) == views::preview;
    std::cout << has_text << " " << has_preview << "\n";
} 

The following is contains an example of code that will not compile since the typesafe operators have not been defined.

#include <stlab/enum_ops.hpp>
 
enum foo { foo_4 = 1 << 2, foo_8 = 1 << 3 };
enum bar { bar_4 = 1 << 2, bar_8 = 1 << 3 };
enum baz { baz_4 = 1 << 2, baz_8 = 1 << 3 };
 
auto stlab_enable_arithmetic_enum(baz) -> std::true_type;
 
int main() {
    foo a{foo_4};
    bar b{bar_8};
    foo c{a + b}; // Error! a and b are different enum types, so result is integral
 
    baz d{baz_4};
    baz e{baz_8};
    baz f{d + e}; // Ok, arithmetic ops enabled for baz, so d + e has type baz
}