View source code Display the source code in std/range/primitives.d from which this page was generated on github. 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. Page wiki View or edit the community-maintained wiki page associated with this page.

Enum std.range.primitives.member isInputRange

Returns true if R is an input range. An input range must define the primitives empty, popFront, and front. The following code should compile for any input range. 

R r;              // can define a range object
if (r.empty) {}   // can test for empty
r.popFront();     // can invoke popFront()
auto h = r.front; // can get the front of the range of non-void type

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

  • r.empty returns false iff there is more data available in the range.
  • r.front returns the current element in the range. It may return by value or by reference. Calling r.front is allowed only if calling r.empty has, or would have, returned false.
  • r.popFront advances to the next element in the range. Calling r.popFront is allowed only if calling r.empty has, or would have, returned false.

Declaration

enum isInputRange(R) = is(typeof((inout int = 0)
{
R r = R.init;
if (r.empty)
{
}
r.popFront();
auto h = r.front;
}
));

Parameters

NameDescription
R type to be tested

Returns

true if R is an InputRange, false if not

Example

struct A {}
struct B
{
    void popFront();
    @property bool empty();
    @property int front();
}
static assert(!isInputRange!A);
static assert( isInputRange!B);
static assert( isInputRange!(int[]));
static assert( isInputRange!(char[]));
static assert(!isInputRange!(char[4]));
static assert( isInputRange!(inout(int)[]));

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