On 2014-06-02 08:08, "Marc Schütz" <schue...@gmx.net>" wrote:
On Monday, 2 June 2014 at 06:56:54 UTC, captaindet wrote:
hi,
i stumbled upon something weird - it looks like a bug to me but
maybe it is a "feature" that is unclear to me.
so i know i can declare function and delegate pointers at module level.
for function pointers, i can initialize with a lambda.
BUT for delegates i get an error - see below
i found out that using module static this(){...} provides a workaround, but why
is this necessary?
also, if there is a good reason after all then the error message should make
more sense.
/det
ps: i know there is a shorthand syntax for this.
----
module demo;
int function(int) fn = function int(int){ return 42; };
// ok
int delegate(int) dg = delegate int(int){ return 666; };
// demo.d(6): Error: non-constant nested delegate literal expression
__dgliteral6
void main(){}
This doesn't work, because a delegate needs a context it can capture,
which is available only inside of a function.
The workaround is either, as Mr Smith suggests, to use a static
constructor, or you can use std.functional.toDelegate() (probably,
didn't test).
FWIW, tried toDelegate() and it does not work either:
--------
module demo2;
import std.functional : toDelegate;
int function(int) fn = function int(int){ return 42; };
// ok
int dg_def(int){ return 666; }
int delegate(int) dg = toDelegate(&dg_def);
// c:\D\DMD2\windows\bin\..\..\src\phobos\std\functional.d(758): Error: Cannot
convert &int delegate(int a0) @system to void* at compile time
// demo2.d(8): called from here: toDelegate(& dg_def)
void main(){}
