% --- start of displayed preamble in the book --- % --- end of displayed preamble in the book --- defaultfont:="ptmr8r"; warningcheck:=0; beginfig(1) draw (0,0)..(1cm,0)..(2cm,1cm)..(3cm,3cm); draw (0,0)--(3cm,3cm); picture p; p=currentpicture; for i within p: if stroked i: if length(pathpart i)>2: draw pathpart i withcolor blue; fi fi endfor; endfig; end;