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digitalmars.D.learn - Foreach over tuple of arrays?

reply Sean Eskapp <eatingstaples gmail.com> writes:
I have a tuple of arrays of different types, but want to call a template
function on each element. How would I do this?

    void foo(T)(T elem)
    {
        ...
    }

I tried like this:

    ArrayTuple!(T) data;
    void iterate(alias func, uint n)()
    {
        static if(n < T.length)
        {
            foreach(elem; data[n])
                func(elem);

            iterate!(func, n + 1)();
        }
    }

Used like this:

    iterate!(foo, 0)();

This doesn't work when passing a delegate as func, however. Is there a way to
circumvent this?
Aug 07 2011
next sibling parent Philippe Sigaud <philippe.sigaud gmail.com> writes:
Hi Sean,

 This doesn't work when passing a delegate as func, however. Is there a way to
 circumvent this?

I tried this with a delegate and a function template, it seems to work: import std.typecons; void bar(T)(ref T elem) { elem = elem+1; } void main() { auto data = tuple([0,1,2,3], [3,2,1], [0,1]); auto foo = (ref int i){ i = i * i;}; writeln(data); foreach(index, range; data.expand) foreach(ref element; range) foo(element); writeln(data); foreach(index, range; data.expand) foreach(ref element; range) bar(element); writeln(data); } data.expand is only needed to get access to the underlying expression template in the 'data' tuple. Your own ArrayTuple!(T) may have other way to do that.
Aug 08 2011
prev sibling parent Philippe Sigaud <philippe.sigaud gmail.com> writes:
Hmm, I just saw your question on SO. Is that nearer to what you ask?
It uses a anonymous template function:


import std.typecons;

void act(alias fun, T...)(ref Tuple!T data)
{
    foreach(index, range; data.expand)
        foreach(ref element; range)
            fun(element);
}

void main()
{
    auto data = tuple([0,1,2,3], [3,2,1], [0,1]);

    writeln(data);

    act!( (i) { return i+1; })(data);

    writeln(data);
}


Philippe
Aug 08 2011