Do N-Space font variants exist?

Question

Programmers often fall back on monospace font variants for legibility, however some programmers blogs I read are starting to laud variable width fonts.

It seems to me that the best of both worlds would be a font where all character widths are small multiples of the space width (so M might be three or four spaces)

Does anyone know if such a font exists, and if so if a variant is available for free?

Answer 1

We can make this a programming question by answering it as such.

In pseudo code:

For each of your installed fonts{
    spacewidth = widthof(space);
    For each character in the current font{
        width[charcode] = widthof[charcode];
    }

    print standarddeviation(spacewidth, width);
}