• d-bugmail puremagic.com (47/47) Jul 23 2013 http://d.puremagic.com/issues/show_bug.cgi?id=10709

d-bugmail puremagic.com writes:

http://d.puremagic.com/issues/show_bug.cgi?id=10709

           Summary: reduce 1-function + no seed, wrong type inference
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Keywords: rejects-valid
          Severity: normal
          Priority: P2
         Component: Phobos
        AssignedTo: monarchdodra gmail.com
        ReportedBy: monarchdodra gmail.com



When reduce is not given a seed, it takes the ranges "front" as a first
element, however, seed's type should be that of the result of calling "fun".

This is relevent for a function for example, that takes int, and returns a
double, or a function that takes operates on const(char)[], and is passed a
string: In both case, reduce will error out when trying to store the result (eg
double) into the seed (eg int).

What is interesting is that "reduce!fun" gets it wrong, but "reduce!(fun,
fun...)" gets it right.

//----
import std.stdio, std.algorithm;

void main(string[] args)
{
    {
        enum foo = "a + 0.5 * b";
        auto r = [0, 1, 2, 3];
        //auto r1 = reduce!foo(r); //<-- HERE
        auto r2 = reduce!(foo, foo,)(r);
        //writeln(r1);
        writeln(r2);
    }

    {
        const(char)[] foo(const(char)[], const(char)[]);
        string[] r = ["hello", "world"];
        //auto r1 = reduce!foo(r); //<-- HERE
        auto r2 = reduce!(foo, foo,)(r);
        //writeln(r1);
        writeln(r2);
    }
}
//----

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