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Function `std.range.dropBackOne`

dropOne is a convenience function which calls range.popFront() and returns range. Unlike popFront, the range argument is passed by copy, not by ref.


						
				R dropBackOne(R)(
				
  R range
				

				)
				

				if (isBidirectionalRange!R);

dropOne makes it easier to pop an element from a range rvalue and then pass it to another function within a single expression, whereas popFront would require multiple statements.

dropBackOne provides the same functionality but instead calls range.popBack().

Example

import std.algorithm.comparison : equal;
import std.algorithm.iteration : filterBidirectional;
import std.container.dlist : DList;

auto dl = DList!int(9, 1, 2, 3, 9);
assert(dl[].dropOne().dropBackOne().equal([1, 2, 3]));

auto a = [1, 2, 3];
writeln(a.dropOne()); // [2, 3]
writeln(a.dropBackOne()); // [1, 2]

string s = "日本語";
import std.exception : assumeWontThrow;
assert(assumeWontThrow(s.dropOne() == "本語"));
assert(assumeWontThrow(s.dropBackOne() == "日本"));

auto bd = filterBidirectional!"true"([1, 2, 3]);
assert(bd.dropOne().equal([2, 3]));
assert(bd.dropBackOne().equal([1, 2]));

Authors

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

License

Boost License 1.0.