metafun question

[Floris van Manen <vm@klankschap.nl>]

it seems that metafun has difficulty understanding the example using
the    vardef self@# expr p =   construct.


! Illegal parameter number in definition of \@MPG@dummy2.
<to be read again> 
                    
<argument> ... p of p enddef; \par vardef self@## 
                                                  expr p = cuta(@##,@##) @##...

\dostartuseMPgraphic ...leuseMPgraphic {#1}{#2}{#3
                                                  }}\elabelgroup 
l.41 \stopuseMPgraphic



why?


i copied the sample of the mp manual:



% interface=english output=pdftex

\starttext


\startuseMPgraphic{dummy2}

vardef cuta(suffix a,b) expr p =
drawarrow p cutbefore bpath.a cutafter bpath.b;
point .5*length p of p
enddef;

vardef self@# expr p =
cuta(@#,@#) @#.c{curl0}..@#.c+p..{curl0}@#.c 
enddef;

beginfig(52);
verbatimtex \def\stk#1#2{$\displaystyle{\matrix{#1\cr#2\cr}}$} etex
circleit.aa(btex\strut Start etex); aa.dx=aa.dy;
circleit.bb(btex \stk B{(a|b)^*a} etex);
circleit.cc(btex \stk C{b^*} etex);
circleit.dd(btex \stk D{(a|b)^*ab} etex);
circleit.ee(btex\strut Stop etex); ee.dx=ee.dy;
numeric hsep;
bb.c-aa.c = dd.c-bb.c = ee.c-dd.c = (hsep,0);
cc.c-bb.c = (0,.8hsep);
xpart(ee.e - aa.w) = 3.8in;
drawboxed(aa,bb,cc,dd,ee);
label.ulft(btex$b$etex, cuta(aa,cc) aa.c{dir50}..cc.c);
label.top(btex$b$etex, self.cc(0,30pt));
label.rt(btex$a$etex, cuta(cc,bb) cc.c..bb.c);
label.top(btex$a$etex, cuta(aa,bb) aa.c..bb.c);
label.llft(btex$a$etex, self.bb(-20pt,-35pt));
label.top(btex$b$etex, cuta(bb,dd) bb.c..dd.c);
label.top(btex$b$etex, cuta(dd,ee) dd.c..ee.c);
label.lrt(btex$a$etex, cuta(dd,bb) dd.c..{dir140}bb.c);
label.bot(btex$a$etex, cuta(ee,bb) ee.c..tension1.3 ..{dir115}bb.c);
label.urt(btex$b$etex, cuta(ee,cc) ee.c{(cc.c-ee.c)rotated-15}..cc.c);
endfig;

\stopuseMPgraphic

\useMPgraphic{dummy2}

\stoptext






//floris