Re: Metafont optional parameters (Owen Lamb)

[Owen Lamb]

Sorry, I just saw this after following a different strategy! For now, I
won't be needing this, but thank you for the advice. It might come in handy
later if there's more MF work to do.

--Owen

On Sun, May 31, 2020 at 5:33 PM Christopher Heckman <
christopher.heckman@asu.edu> wrote:

> On Sun, May 31, 2020 at 12:50 AM <lilypond-devel-request@gnu.org> wrote:
> >
> > Date: Sat, 30 May 2020 15:41:31 -0700
> > From: Owen Lamb <owendlamb@gmail.com>
> > To: Werner LEMBERG <wl@gnu.org>, lilypond-devel@gnu.org
> > Subject: Metafont optional parameters
> > Message-ID:
> >         <CAHpoxV-+XVN3x5QU6gh0yMkGXp6tSu4t-y7H4QVGSWdx=
> UFnSA@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
>
>