Hans et al,

`Let me try to be more specific. Here is a file which is very typical of`

`the way I draw graphs for my mathematics classes. When you compile, you`

`will see the graph of the absolute value of x-1. That is, it draws the`

`graph of y=|x-1|, but only after clipping it to the cpath. What I`

`would like to do is draw the graph with the drawdblarrow command so`

`that the graph of the absolute value ends in arrowheads. So, I want to`

`clip the graph to the bounding box, save the picture, null the picture,`

`then somehow extract the path into the variable F in its clipped form`

`(not the original path F that extends outside the clip path) so that I`

`can replace the command draw pic with drawdblarrow F.`

beginfig(0); numeric a, c; a=1; % define function f(x)=|x-a| vardef f(expr x)= abs(x-a) enddef; % draw line with given point and slope path F; F:=(-5,f(-5)); for x=-5 step 1 until 5: F:=F--(x,f(x)); endfor; % initialize scale numeric u; 10u=3in; % the line F:=F scaled 1u; draw F withcolor blue; % clipping path path cpath; cpath:=(-5,-5)--(5,-5)--(5,5)--(-5,5)--cycle; cpath:=cpath scaled 1u; % clip and save current picture picture pic; clip currentpicture to cpath; pic:=currentpicture; currentpicture:=nullpicture; % erase currentpicture currentpicture:=nullpicture; % draw grid for k=-5u step 1u until 5u: draw (-5u,k)--(5u,k) withcolor 0.85white; draw (k,-5u)--(k,5u) withcolor 0.85white; endfor; % draw axes drawarrow (-5u,0)--(5u,0); drawarrow (0,-5u)--(0,5u); % label axes label.rt(btex $x$ etex, (5.2u,0)); label.top(btex $y$ etex, (0,5.2.u)); label.bot(btex $5$ etex, (5u,0)); label.lft(btex $5$ etex, (0,5u)); % redraw line draw pic; endfig; end. _______________________________________________ ntg-context mailing list ntg-context@ntg.nl http://www.ntg.nl/mailman/listinfo/ntg-context