% --- start of displayed preamble in the book ---
input hatching;
% --- end of displayed preamble in the book ---
% graphic converted to gray in book using 'color2gray'
defaultfont:="ptmr8r";
warningcheck:=0;
beginfig(1)
path p;
p:=unitsquare xscaled 30mm yscaled 15mm;
hatchfill p withcolor red
            withcolor (45,2mm,-.5bp)
            withcolor (-45,2mm,-.5bp);
endfig;
end;