Superscript/subscript/fractions & software to aid in design


I never finished any fonts until recently and so I never got to the stage of designing numbers before. While completing all the numeral sets I came to realize that the fractals require their very own set which is distinct from superscript/subscript. I guess I should have realized, and yet I was surprised at the amount of work required to complete all numeral sets.

Help with OpenType fractions


If I generate an OTF font, and I have a glyph created for onehalf, will "1 slash 2" automatically be replaced by onehalf, or do I need to build a feature for it?

Tried building a feature, but an "aborting because of errors" error:

feature frac {
lookup frac1 {
sub one slash 2 by onehalf;
} frac1;
lookup frac1;
} frac;

Also, what is the easiest way to code for all "(number) slash (number)" to change into nut fractions? I'd like this to work up into the thousands (333/1028 for example). Creating a "sub" line of code for every possible fraction is obviously impractical.

Old Style Fractions


I read in a book "Book Typography: A Designer's Manual" that fractions near old style figures should be minimized if they seem to large.

So I think: isn't it possible with OT features?

I could make additional sets of numerators and denominators - one.numr.osf etc. and fraction.osf that would be a little bit smaller to harmonize with lowercase glyphs.

Than some changes to the frac feature should be made.
Here's my frac (auto-generated from Glyphs) :

lookup FRAC {
sub slash by fraction;
lookup HOCH {
sub [zero one two three four five six seven eight nine] by [zero.numr one.numr two.numr three.numr four.numr five.numr six.numr seven.numr eight.numr nine.numr];
lookup TIEF {

How do I script Swash letters, alternates etc.?


I've recently learned how to use Fontlab Studio 5, and I also learned how to script ligatures. But I noticed Illustrator for example has more buttons in the type tool section: Standard Ligatures, Contextual Ligatures, Discretionary Ligatures, Swash, Stylistic Alternates, Titling Alternates, Ordinals and Fractions.

So out of that list, I only know how to script the standard ligatures. Does anyone know how to script the others, or do you know a source to learn about it? Most font families contain all the ligatures and swash letters as seperate fonts rather than putting it into a single font (OpenType). Is there a reason for doing this?