Re: How to get type returned by e.g. std.algorithm.iteration.filter

[Christian Köstlin via Digitalmars-d-learn]

On 19.05.19 20:38, Jacob Carlborg wrote:
On 2019-05-19 15:36, Christian Köstlin wrote:
Unfortunately I have no idea how to even store the result of this 
search in an attribute of ByMinimum, as I cannot writeout its type.

In general you can use `typeof(<expression>)`, where `<expression>` is 
the expression you want to get the type of.

Thanks for the hint. The best I could come up with this is:

#!/usr/bin/env rdmd
import std.stdio;
import std.algorithm;
import std.typecons;
import std.array;
import std.range;
import std.traits;

auto byMinimum(Ranges)(Ranges ranges)
{
    auto getNonEmpty()
    {
        return ranges.filter!("!a.empty");
    }

    auto minimumOfRanges(Ranges)(Ranges ranges) {
        // dfmt off
        return ranges
            .map!(range => tuple!("range", "line")(range, range.front))
            .minElement!("a.line");
        // dfmt on
    }
    auto nonEmpty = getNonEmpty;
    ReturnType!(minimumOfRanges!(typeof(nonEmpty))) minRangeAndLine;
    struct ByMinimum(Ranges)
    {
        bool empty()
        {
            return nonEmpty.empty;
        }

        auto front()
        {
            minRangeAndLine = minimumOfRanges(nonEmpty);
            return minRangeAndLine;
        }

        void popFront()
        {
            minRangeAndLine.range.popFront;
            nonEmpty = getNonEmpty;
        }
    }
    return ByMinimum!(Ranges)();
}

void main(string[] files)
{
    foreach (n; files[1 .. $].map!(name => 
File(name).byLine(No.keepTerminator)).array.byMinimum)
    {
        writeln(n.line);
    }
}


Still it looks a little clumsy. Any ideas?

--
Christian