On Sun, May 31, 2020 at 12:50 AM <[email protected]> wrote: > > Date: Sat, 30 May 2020 15:41:31 -0700 > From: Owen Lamb <[email protected]> > To: Werner LEMBERG <[email protected]>, [email protected] > Subject: Metafont optional parameters > Message-ID: > <CAHpoxV-+XVN3x5QU6gh0yMkGXp6tSu4t-y7H4QVGSWdx=uf...@mail.gmail.com> > Content-Type: text/plain; charset="UTF-8" > > Hi all, > > I'd like to add an optional parameter for smuflcode to fet_beginchar, so > that I don't have to take two lines redeclaring the variable in every > glyph. Ideally, it won't have to be optional once every character has it, > but in the meantime, it would help with testing individual characters' new > encodings. > > I wasn't able to find whether MF supports optional parameters, only that > certain built-in functions have them. Does anyone with MF experience know > if it does, and, if so, how to put one in? > > Thanks, > Owen
The METAFONTbook shows how to handle a variable number of arguments to a macro. It gives examples about how to write max() with a variable number of parameters. If you want to allow at least one parameter, then look at Appendix D (Dirty Tricks), trick #2 (pp. 290-291 in my version): vardef max(text t) = let switch_ = firstset_; for u = t: switch_ u > u_: u_ := u ;fi endfor u_ enddef; def firstset_ primary u = setu_ u; let switch_ = if; if false: enddef. If you want to allow at least two parameters (but not one), it's a bit easier; the code is on page 266 of Appendix B (Basic Operations): vardef max(expr u)(text t) = % t is a list of numerics, pairs or strings save u_; set u_ u; for uu = t: if uu > u_: u_ := uu; fi endfor u_ enddef; def setu_ primary u = if pair u: pair u_ elseif string u: string u_ fi; u_ = u enddef; Any typos are my fault, not DEK's. --- Christopher Heckman
