Feature proposal: Enumflagset (zig bit flags type) #4185
Description
Below is what I imagine the entry in the zig docs would look like if this feature was implemented.
Edit: added "tag type" and "_SPARE field" to the example below.
Enumflagset
Zig provides enumflagset as a safer and more ergonomic way to implement bit flags, as opposed to using plain integers.
An enumflagset behaves as an integer that is configured with a set of default (power of 2) values, that can be combined with set operations only: union, intersection, complement and equality. (respectively, bitwise: or, and, not, equals). These set operations are closed for the enumflagset, except the equals operator which can accept a 0 as an operand.
The complement operation (bitwise not) is restricted to the bits in use, so masking is not necessary.
// specificying an uint as the tagtype is mandatory
const WidgetAnchor = enumflagset(u4){
LEFT = 1,
RIGHT = 2,
TOP = 4,
BOTTOM = 8,
// Mandatory field, must be equal to the complement of the bitwise or of all the other members
_SPARE = 0,
// If tagtype was u6, compiler would force you to write:
// _SPARE = 16 + 32,
// compile error: must be power of 2
ERR_EXAMPLE_1 = 3,
// compile error: cannot be zero
// (only SPARE can be zero if all the bits of the tagtype are used)
ERR_EXAMPLE_2 = 0,
// compile error: duplicate of "LEFT"
ERR_EXAMPLE_3 = 1,
}
const my_anchor : WidgetAnchor = .LEFT | .RIGHT;
const isAnchoredLeft = (my_anchor & .LEFT) != 0;
const isNotAnchoredLeft = (my_anchor & .LEFT) == 0;
// compile error: only bitwise operators (or, and, not) are allowed for enumflags
const my_anchor2 : WidgetAnchor = my_anchor + .LEFT;
// compile error: Both operands of bitwise-or must be WidgetAnchor members.
const my_anchor3 : WidgetAnchor = my_anchor | 4;