[Issue 11082] std.algorithm.join of a dynamic array of fixed-size arrays

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=11082



--- Comment #7 from bearophile_hugs at eml.cc 2013-09-21 13:18:09 PDT ---
(In reply to comment #6)

> But is it worth doing for every other algorithm, and every container type?

Probably not. But I think it's worth doing for a small subset of algorithms, as
std.algorithm.join.

Regarding containers, fixed sized arrays are built-ins, and they are supposed
to be used often, so it's not unreasonable to handle them differently/better
than library-defined containers.


> You have to do:
> 
> data.map!((ref a => a[])).join.writeln;
> 
> Unfortunately shorthand lambdas and unaryFun default to pass-by-value, so you
> get a stack copy of your static array, which you then slice just as it goes out
> of scope.

DMD has to give a compile-time error for such situation. I think there's an
enhancement request opened on that.

Joining a sequence of fixed-size arrays is a commonly done operation (in my
code), and that map+join code is bug-prone. Your code too has a small mistake:


import std.algorithm: join;
import std.stdio, std.algorithm;
void main() {
    int[2][] data = [[1, 2]];
    data.map!((ref a) => a[]).join.writeln;
}

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