transforming character into rule in LaTeX

[Daniel Molina]

On 8/9/20 17:37, Daniel Molina wrote:
>
> My original problem is to substitute any subformula with a rule of a
> specific color.
>

As a workaround I resolved the problem using an extended mathpalette in
LuaTeX as explained in

https://tex.stackexchange.com/questions/404286/the-phantom-directive-does-not-do-what-i-expect

by egreg. In addition I used a colorbox and the same color for the font.
Apart from being around 3 times slower than LaTeX, it works.

Regards,

Daniel