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Template 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.
Arguments
template isBitFlagEnum(E);
Example
enum A
{
None,
A = 1<<0,
B = 1<<1,
C = 1<<2,
D = 1<<3,
}
static assert(isBitFlagEnum!A);
enum B
{
A,
B,
C,
D // D == 3
}
static assert(!isBitFlagEnum!B);
enum C: double
{
A = 1<<0,
B = 1<<1
}
static assert(!isBitFlagEnum!C);
}
/**
A typesafe structure for storing combination 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