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 hasLvalueElements
Tests whether the range R has lvalue elements. These are defined as
elements that can be passed by reference and have their address taken.
The following code should compile for any range with lvalue elements.
void passByRef(ref ElementType!R stuff); ... static assert(isInputRange!R); passByRef(r.front); static if (isBidirectionalRange!R) passByRef(r.back); static if (isRandomAccessRange!R) passByRef(r[0]);
Declaration
enum hasLvalueElements(R) = isInputRange!R && is(typeof((inout int = 0)
{
void checkRef(ref ElementType!R stuff);
R r = R.init;
checkRef(r.front);
static if (isBidirectionalRange!R)
{
checkRef(r.back);
}
static if (isRandomAccessRange!R)
{
checkRef(r[0]);
}
}
));
Example
import std.range : iota, chain; static assert( hasLvalueElements!(int[])); static assert( hasLvalueElements!(const(int)[])); static assert( hasLvalueElements!(inout(int)[])); static assert( hasLvalueElements!(immutable(int)[])); static assert(!hasLvalueElements!(typeof(iota(3)))); static assert(!hasLvalueElements!( string)); static assert( hasLvalueElements!(dstring)); static assert(!hasLvalueElements!( char[])); static assert( hasLvalueElements!(dchar[])); auto c = chain([1, 2, 3], [4, 5, 6]); static assert( hasLvalueElements!(typeof(c)));
Authors
Andrei Alexandrescu, David Simcha, and Jonathan M Davis. Credit for some of the ideas in building this module goes to Leonardo Maffi.