\starttext
\stopuseMPgraphic
\startuseMPgraphic{name_a}
beginfig(1)
w = 3cm;			% width
h = w*1.2;			% height
xheight = 1/1.5;	% hauteur de x
eheight = 1/3;		% hauteur de barre (1=top, 0=bottom)
slant = 0;			% slanted (-1 > backward > 0 > italic > 1)
	y1 = y2 = 0;
	x1 = x2-w = 0;
	y1+y3 = h;
	x3 - 1*slant = (x2+x1)/2;
	y4 = y5 = y3*eheight;
	z4=whatever[z1,z3];
	z5=whatever[z2,z3];

	pickup pencircle xscaled 15 rotated 30;
	draw z1--z3--z2;
	draw z4{dir 30}..{dir 30}z5;
	%labels(range 1 thru 5);
endfig;
\stopuseMPgraphic

\useMPgraphic{name_a}

\stoptext