Another task

[bearophile]

Now and then I like to test Phobos with simple tasks, to see how it's going.

This simple task is to create a dynamic array of pairs (tuples) like:
[(10,"aa"), (30,"bb"), (50,"cc")]

from the associative array:
[1:'a', 2:'b', 3:'c']

If possible read things lazily from the associative array.

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Idiomatic Python2 solution (iteritems is lazy):

>>> d = {1:'a', 2:'b', 3:'c'}
>>> [(k*10, v*2) for k,v in d.iteritems()]
[(10, 'aa'), (20, 'bb'), (30, 'cc')]

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D2 lazy solution without map():

import std.stdio, std.typecons;
void main() {
    auto aa = [1:'a', 2:'b', 3:'c'];
    Tuple!(int, string)[] r;
    foreach (k, v; aa)
        r ~= tuple(k*10, ""~v~v);
    writeln(r);
}

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Alternative D2 lazy solution without append and map():

import std.stdio, std.typecons;
void main() {
    auto aa = [1:"a", 2:"b", 3:"c"];
    auto r = new Tuple!(int, string)[aa.length];
    int count = 0;
    foreach (k, v; aa)
        r[count++] = tuple(k*10, v~v);
    writeln(r);
}

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Now to test Phobos a little, is it easy to write a D2 lazy version that uses map()? Are you able to write it? How many tries needs a D2 programmer with about a month of D2 programming experience to write a correct version that uses map()?

Bye,
bearophile