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Function std.algorithm.mutation.swap
Swaps lhsrhslhsrhsopAssign, nor any other function. T
need not be assignable at all to be swapped.
If lhsrhs
lhsrhsT is a struct or union, then
its fields must also all be (recursively) mutable.
Prototype
void swap(T)( T lhs, T rhs ) pure nothrow @nogc @trusted if (isBlitAssignable!T && !is(typeof(lhs.proxySwap(rhs))));
Parameters
| Name | Description |
|---|---|
| lhs | Data to be swapped with |
| rhs | Data to be swapped with |
Example
// Swapping POD (plain old data) types:
int a = 42, b = 34;
swap(a, b);
assert(a == 34 && b == 42);
// Swapping structs with indirection:
static struct S { int x; char c; int[] y; }
S s1 = { 0, 'z', [ 1, 2 ] };
S s2 = { 42, 'a', [ 4, 6 ] };
swap(s1, s2);
assert(s1.x == 42);
assert(s1.c == 'a');
assert(s1.y == [ 4, 6 ]);
assert(s2.x == 0);
assert(s2.c == 'z');
assert(s2.y == [ 1, 2 ]);
// Immutables cannot be swapped:
immutable int imm1, imm2;
static assert(!__traits(compiles, swap(imm1, imm2)));
Example
// Non-copyable types can still be swapped.
static struct NoCopy
{
this(this) { assert(0); }
int n;
string s;
}
NoCopy nc1, nc2;
nc1.n = 127; nc1.s = "abc";
nc2.n = 513; nc2.s = "uvwxyz";
swap(nc1, nc2);
assert(nc1.n == 513 && nc1.s == "uvwxyz");
assert(nc2.n == 127 && nc2.s == "abc");
swap(nc1, nc1);
swap(nc2, nc2);
assert(nc1.n == 513 && nc1.s == "uvwxyz");
assert(nc2.n == 127 && nc2.s == "abc");
// Types containing non-copyable fields can also be swapped.
static struct NoCopyHolder
{
NoCopy noCopy;
}
NoCopyHolder h1, h2;
h1.noCopy.n = 31; h1.noCopy.s = "abc";
h2.noCopy.n = 65; h2.noCopy.s = null;
swap(h1, h2);
assert(h1.noCopy.n == 65 && h1.noCopy.s == null);
assert(h2.noCopy.n == 31 && h2.noCopy.s == "abc");
swap(h1, h1);
swap(h2, h2);
assert(h1.noCopy.n == 65 && h1.noCopy.s == null);
assert(h2.noCopy.n == 31 && h2.noCopy.s == "abc");
// Const types cannot be swapped.
const NoCopy const1, const2;
static assert(!__traits(compiles, swap(const1, const2)));