How to pass a tex formatted string as a parameter to a metapost macro?

Question

For example I want to pass the string \huge$p_2f_1$

To the macro

vardef macro(expr point, lab)=
    label(btex lab, point);
enddef;

Answer 1

The btex ... etex tags convert the TeX expression between them into a picture, not a string.

You could use something like this

vardef macro(expr point, lab)=
    label(lab, point);
enddef;

and then

macro(origin, btex your TeX code etex);

Or, assuming you're using LuaLaTeX and luamplib with the option \mplibtextextlabel{enable}, then the text argument of label is indeed supposed to be a string and you can enter something like this when you use the macro above:

macro(origin, "your TeX code");