Modifing local variables with anonymous delegate?

[Adam D. Ruppe]

On Thursday, 26 December 2013 at 23:23:02 UTC, Gordon wrote:
> But the "b" in "main" retains its original value of 42.

Try printing the b in main again AFTER printing c. You should see 
the change.

std.algorithm for the most part doesn't actually do any of its 
calculations until it has to. This allows it to save speed 
skipping work it doesn't need, and make it possible to map 
infinite series and stuff like that.

So the line c = map....; just prepares the calculation, it 
doesn't actually run the function. The writeln(c) forces 
evaluation. You can also force evaluation immediately by calling 
.array on the thing, which calculates it and puts the result in a 
new array.