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Enum member std.typecons.isBitFlagEnum
Detect whether an enum is of integral type and has only "flag" values (i.e. values with a bit count of exactly 1). Additionally, a zero value is allowed for compatibility with enums including a "None" value.
enum isBitFlagEnum(E)
= E .min >= 0 && ()
{
static foreach (immutable flag; EnumMembers!E)
{
{
Base value = flag;
value &= value - 1;
if (value != 0)
return false;
}
}
return true;
}
();
Example
enum A
{
None,
A = 1 << 0,
B = 1 << 1,
C = 1 << 2,
D = 1 << 3,
}
static assert(isBitFlagEnum!A);
Example
Test an enum with default (consecutive) values
enum B
{
A,
B,
C,
D // D == 3
}
static assert(!isBitFlagEnum!B);
Example
Test an enum with non-integral values
enum C: double
{
A = 1 << 0,
B = 1 << 1
}
static assert(!isBitFlagEnum!C);
}
/**
A typesafe structure for storing combinations of enum values.
This template defines a simple struct to represent bitwise OR combinations of
enum values. It can be used if all the enum values are integral constants with
a bit count of at most 1, or if the `unsafe` parameter is explicitly set to
Yes.
This is much safer than using the enum itself to store
the OR combination, which can produce surprising effects like this:
enum E { A = 1 << 0, B = 1 << 1 } E e = E.A | E.B; // will throw SwitchError final switch (e) { case E.A: return; case E.B: return;
Authors
Andrei Alexandrescu, Bartosz Milewski, Don Clugston, Shin Fujishiro, Kenji Hara
License
Copyright © 1999-2022 by the D Language Foundation | Page generated by ddox.