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std.range.primitives.pop_front - multiple declarations

Function popFront

Implements the range interface primitive popFront for built-in arrays. Due to the fact that nonmember functions can be called with the first argument using the dot notation, array.popFront is equivalent to popFront(array). For narrow strings, popFront automatically advances to the next code point.

Prototype

void popFront(T)(
  T[] a
) pure nothrow @nogc @safe
if (!isNarrowString!(T[]) && !is(T[] == void[]));

Example

auto a = [ 1, 2, 3 ];
a.popFront();
assert(a == [ 2, 3 ]);

Function popFrontN

Eagerly advances r itself (not a copy) up to n times (by calling r.popFront). popFrontN takes r by ref, so it mutates the original range. Completes in Ο(1) steps for ranges that support slicing and have length. Completes in Ο(n) time for all other ranges.

Prototype

size_t popFrontN(Range)(
  Range r,
  size_t n
)
if (isInputRange!Range);

Returns

How much r was actually advanced, which may be less than n if r did not have at least n elements.

popBackN will behave the same but instead removes elements from the back of the (bidirectional) range instead of the front.

Example

int[] a = [ 1, 2, 3, 4, 5 ];
a.popFrontN(2);
assert(a == [ 3, 4, 5 ]);
a.popFrontN(7);
assert(a == [ ]);

Example

import std.algorithm : equal;
import std.range : iota;
auto LL = iota(1L, 7L);
auto r = popFrontN(LL, 2);
assert(equal(LL, [3L, 4L, 5L, 6L]));
assert(r == 2);

Example

int[] a = [ 1, 2, 3, 4, 5 ];
a.popBackN(2);
assert(a == [ 1, 2, 3 ]);
a.popBackN(7);
assert(a == [ ]);

Example

import std.algorithm : equal;
import std.range : iota;
auto LL = iota(1L, 7L);
auto r = popBackN(LL, 2);
assert(equal(LL, [1L, 2L, 3L, 4L]));
assert(r == 2);

Authors

Andrei Alexandrescu, David Simcha, and Jonathan M Davis. Credit for some of the ideas in building this module goes to Leonardo Maffi.

License

Boost License 1.0.

Comments