Perm

A struct that generates all possible permutations of a sequence.

Notes:

Permutations are output in undefined order.

The array returned by front is recycled across iterations. To preserve it across iterations, wrap this range using map!"a.dup" or map!"a.idup".

struct Perm (

) {

this(U input);

const(T)[] front [@property getter];

void popFront();

bool empty [@property getter];

size_t length [@property getter];

typeof(this) save [@property getter];

}

Constructors

this this(U input): Generate permutations from an input range. * Create a duplicate of this sequence * so that the original sequence is not modified.

Members

Functions

popFront void popFront(): Get the next permutation in the sequence. This will overwrite the contents of the array returned by the last call to front.

Properties

empty bool empty [@property getter]
front const(T)[] front [@property getter]: Returns the current permutation. The array is const because it is recycled across iterations and modifying it would destroy the state of the permutation generator.
length size_t length [@property getter]: The number of permutations left.
save typeof(this) save [@property getter]

Only supports iterating over up to size_t.max permutations. This means the max permutation length is 12 on 32-bit machines, or 20 on 64-bit. This was a conscious tradeoff to allow this range to have a length of type size_t, since iterating over such huge permutation spaces would be insanely slow anyhow.

Examples

double[][] res;
auto perm = map!"a.dup"(Perm!(double)([1.0, 2.0, 3.0][]));
foreach(p; perm) {
     res ~= p;
}

auto sorted = sort(res);
assert(sorted.canFind([1.0, 2.0, 3.0]));
assert(sorted.canFind([1.0, 3.0, 2.0]));
assert(sorted.canFind([2.0, 1.0, 3.0]));
assert(sorted.canFind([2.0, 3.0, 1.0]));
assert(sorted.canFind([3.0, 1.0, 2.0]));
assert(sorted.canFind([3.0, 2.0, 1.0]));
assert(sorted.length == 6);

The OpenD Programming Language

Perm

Constructors

Members

Functions

Properties

Bugs

Examples

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