Hi,

I defined a macro definition in metafun, and draw figures using \startbuffer[] … \stopbuffer and \processMPbuffer[].
As you see in the attached code, the same macro definition is used repeatedly by changing the numeric argument. 
Is there a better way to simplify the code, for example, using \dorecurse and recurselevel?

Thank you for reading.

Best regards,

Dalyoung

\startbuffer[UDBasic]
pair A,B,C,D;
pair E, F, G, H;
path p,q;
numeric ang,maxNum;
u:=1in;
A=(.95*TextWidth,u); B=(0,u); C=(0,0); D=(.95*TextWidth,0);
p := A--B--C--D;
q := (TextWidth,1.5u)--(0,1.5u)--(0,-.5u)--(TextWidth,-.5u)--cycle;
z0=(.1u,0);
vardef nextPt (expr M,N) =
if ypart(N) = 0:
H := whatever[N, N + dir(.5*angle(M-N))*u] = whatever[A,B];
else:
H := whatever[N, N + dir(.5*angle(M-N))*u] = whatever[C,D];
fi;
H
enddef;

def grayUD(expr i) =
draw G -- if ypart(B)=ypart(G): B -- C else: C -- B fi --z[i];
filldraw z[i]+2*(G-z[i])*u -- z[i] -- z[i+1] -- z[i+1]+(G-z[i])*u -- cycle withcolor .75white;
draw G -- z[i+1] dashed evenly;
draw z[0] for k=0 upto i: --z[k] endfor dashed evenly;
clip currentpicture to q;
enddef;

def linesUD(expr i) =
draw p;
draw z0 for k=0 upto i+1: --z[k] endfor dashed evenly;
setbounds currentpicture to boundingbox q;
enddef;
\stopbuffer

\startbuffer[UDpts]
ang := 40;
z[1] = whatever[z[0], z[0]+dir(ang)*u] = whatever[A,B];
G := whatever[z[0], z[0]+dir(2*ang)*u] = whatever[A,B];
for k = 2 upto 20:
z[k] = nextPt(z[k-2],z[k-1]);
maxNum := k;
exitif xpart(z[k]) > TextWidth;
endfor;
\stopbuffer
\startbuffer[UD0]
draw p;
setbounds currentpicture to boundingbox q;
\stopbuffer
\startbuffer[UD1]
grayUD(0);
\stopbuffer
\startbuffer[UD11]
linesUD(0);
\stopbuffer
\startbuffer[UD2]
G := z0;
grayUD(1)
\stopbuffer
\startbuffer[UD21]
linesUD(1);
\stopbuffer
\startbuffer[UD3]
G := z1;
grayUD(2);
\stopbuffer
\startbuffer[UD31]
linesUD(2);
\stopbuffer
\startbuffer[UD4]
G := z2;
grayUD(3);
\stopbuffer
\startbuffer[UD41]
linesUD(3);
\stopbuffer
\startbuffer[UD5]
G := z3;
grayUD(4);
\stopbuffer
\startbuffer[UD51]
linesUD(4);
\stopbuffer
\startbuffer[UDFinal]
draw p;
draw z0--z1--z2--z3--z4--z5--z6--z7--z8 dashed evenly;
setbounds currentpicture to boundingbox q;
\stopbuffer
\starttext
\processMPbuffer[UDBasic,UDpts,UD0]
\processMPbuffer[UDBasic,UDpts,UD1]
\processMPbuffer[UDBasic,UDpts,UD11]
\processMPbuffer[UDBasic,UDpts,UD2]
\processMPbuffer[UDBasic,UDpts,UD21]
\processMPbuffer[UDBasic,UDpts,UD3]
\processMPbuffer[UDBasic,UDpts,UD31]
\processMPbuffer[UDBasic,UDpts,UD4]
\processMPbuffer[UDBasic,UDpts,UD41]
\processMPbuffer[UDBasic,UDpts,UD5]
\processMPbuffer[UDBasic,UDpts,UD51]
\processMPbuffer[UDBasic,UDpts,UDFinal]
\stoptext