Normally one wants to use a full typesetting system, and access to fonts with a rich variety of symbols to typeset mathematics. But sometimes you don't.
Plain text, restricted to ASCII, still has its uses. It is possible to lay out the 2-dimensional mathematical notations as a kind of ‘ASCII-art’. Historically in the days before GUI workbook-style interfaces most Computer Algebra systems would use this kind of layout, and they can usually still be persuaded to use this style even in current versions.
I've just made available a very old stylesheet, it was I think one of the first XSLT 2 stylesheets that I wrote, which renders MathML in this style. It still does not do all of MathML3 (or 2) presentation MathML, but I intend to extend it as time permits.
The stylesheet is available on google code and some examples running against the MathML test suite are shown below.
The google code project also has the htmlparse styesheet discussed previously in this blog, and a perhaps more serious XSLT stylesheet to render MathML via TeX, again that will be extended to cover most of MathML3, as part of the MathML CR implementation phase – something to do over the Christmas break. Documentation of exactly what's in the project will be added eventually, it's only been running a day.
infinity ---- \ ) x / i ---- i = 0
1 / x | e dx / 0
2 2 1 x + y x + 2yx + y 2 2 3 2 2 3 x + y x + 2yx + y x + 3yx + 3y x + y 2 2 3 2 2 3 4 3 2 2 3 4 x + 2yx + y x + 3yx + 3y x + y x + 4yx + 6y x + 4y x + y 3 2 2 3 4 3 2 2 3 4 5 4 2 3 3 2 4 5 x + 3yx + 3y x + y x + 4yx + 6y x + 4y x + y x + 5yx + 10y x + 10y x + 5y x + y
_ 1 + \|5 --------- 2