Re: why is this cast necessary?

[Ellery Newcomer]

On 06/07/2010 10:02 PM, Graham Fawcett wrote:

Hi folks,

This program works as expected in D2:

     import std.stdio;
     import std.algorithm;

     T largestSubelement(T)(T[][] lol) {
       alias reduce!"a>b?a:b" max;
       return cast(T) max(map!max(lol));   // the cast matters...
     }

     void main() {
       auto a = [[1,2,3],[4,5,6],[8,9,7]];
       assert (largestSubelement(a) == 9);

       auto b = ["howdy", "pardner"];
       assert (largestSubelement(b) == 'y');

       auto c = [[1u, 3u, 45u, 2u], [29u, 1u]];
       assert (largestSubelement(c) == 45u);
     }

But if I leave out the 'cast(T)' in line 7, then this program will not
compile:

lse.d(6): Error: cannot implicitly convert expression
                  (reduce(map(lol))) of type dchar to immutable(char)
lse.d(14): Error: template instance
                   lse.largestSubelement!(immutable(char)) error
instantiating

Where did the 'dchar' came from? And why does the cast resolve the issue?

Best,
Graham

Curious. in std.array, for string types front is defined as

dchar front(A)(A a);

ick. unicode.