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Enum member std.range.primitives.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.
enum hasLvalueElements(R)
= isInputRange!R && is(typeof(isLvalue(lvalueOf!R .front))) && (!isBidirectionalRange!R || is(typeof(isLvalue(lvalueOf!R .back)))) && (!isRandomAccessRange!R || is(typeof(isLvalue(lvalueOf!R[0]))));
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]);
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.
License
Copyright © 1999-2022 by the D Language Foundation | Page generated by ddox.