% --- start of displayed preamble in the book ---
input boxes
% --- end of displayed preamble in the book ---
defaultfont:="ptmr8r";
warningcheck:=0;
beginfig(1)
boxjoin(a.n=b.s-(20,60));
boxit.one("One");circleit.two("Two");
drawboxes(one,two);
drawarrow one.c--two.c
 cutbefore bpath one cutafter bpath two;
boxjoin();
boxit.three("Three");three.w=one.e+(20,0);
fill bpath three withcolor blue;
draw bpath three;draw pic(three) withcolor white;
endfig;
end;