Menu
Search

API Documentation

version 2.105.0

overview

View source code
Display the source code in std/range/primitives.d from which this page was generated on github.
Report a bug
If you spot a problem with this page, click here to create a Bugzilla issue.
Improve this page
Quickly fork, edit online, and submit a pull request for this page. Requires a signed-in GitHub account. This works well for small changes. If you'd like to make larger changes you may want to consider using local clone.

Enum member std.range.primitives.isBidirectionalRange

Returns true if R is a bidirectional range. A bidirectional range is a forward range that also offers the primitives back and popBack. The following code should compile for any bidirectional range.

enum isBidirectionalRange(R) = isForwardRange!R && is(typeof((R r) => r.popBack)) && (is(typeof((return ref R r) => r.back)) || is(typeof((return ref R r) ref => r.back))) && is(typeof(R.init.back.init) == ElementType!R);

The semantics of a bidirectional range (not checkable during compilation) are assumed to be the following (r is an object of type R):

  • r.back returns (possibly a reference to) the last element in the range. Calling r.back is allowed only if calling r.empty has, or would have, returned false.

See Also

The header of std.range for tutorials on ranges.

Example

alias R = int[];
R r = [0,1];
static assert(isForwardRange!R);           // is forward range
r.popBack();                               // can invoke popBack
auto t = r.back;                           // can get the back of the range
auto w = r.front;
static assert(is(typeof(t) == typeof(w))); // same type for front and back

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.