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digitalmars.D.learn - Avoiding Range Postblits

reply =?UTF-8?B?Ik5vcmRsw7Z3Ig==?= <per.nordlow gmail.com> writes:


I'm constructing an array of ranges that are used further down in 
the function contextOf.

The expression

     nds.map!(nd => gr.dijkstraWalker(nd, ...)).array;

however triggers postblits for the range DijkstraWalker returned 
by the instantiator dijkstraWalker.

Can this be avoided somehow?

I'm guessing that move construction plays a key role here.

Note that I can't remove the .array as they required to be 
l-values because their iteration to have side-effects at the end 
of the function contextOf().
Feb 18 2015
next sibling parent ketmar <ketmar ketmar.no-ip.org> writes:
On Wed, 18 Feb 2015 22:51:17 +0000, Nordl=C3=B6w wrote:

 Can this be avoided somehow?
i don't think so. you can use heap-allocated structs, of course, or maybe=20 `RefCounted!` can do the trick, but i not tried it.=
Feb 18 2015
prev sibling parent =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 02/18/2015 02:51 PM, "Nordlöw" wrote:

 I'm guessing that move construction plays a key role here.
move() does avoid the post-blit but you get many destructions in return: import std.stdio; import std.algorithm; import core.memory; struct Graph {} struct DW { int i; this(int i) { writefln(" this() for %s", i); this.i = i; } ~this() { writefln("~this() for %s", i); } this(this) { writefln("this(this) for %s", i); assert(false, "Oops"); } } DW dw(Graph gr, int i) { return DW(i); } void main() { auto gr = Graph(); auto arr = [ 1, 2, 3 ]; auto dws = new DW[arr.length]; foreach (i, el; arr) { auto source = gr.dw(el); move(source, dws[i]); } writeln(dws); } The output: this() for 1 ~this() for 0 ~this() for 0 this() for 2 ~this() for 0 ~this() for 0 this() for 3 ~this() for 0 ~this() for 0 [DW(1), DW(2), DW(3)] ~this() for 3 ~this() for 2 ~this() for 1 Ali
Feb 18 2015