[metapost] mpgraph grdrawarrow problem.

[Scott Ballantyne]

This is using Metapost version 1.208.

It seems there may be a bug in the gdrawarrow macro. I have a straight
line sloping downwards to the right. However the arrow drawn is
pointing vertically down, instead of along the line, as it should
be. This illustrates the problem:

beginfig (1)
  draw begingraph(6in, 2in)
    setrange ((0,whatever),(12,whatever));
    gdrawarrow (0,50)--(2,50)--(10,-850);
  endgraph;
endfig;
end

Does anyone know of a fix or workaround for this?

I was also surprised that mpgraph complains about numbers in the
thousands - 8500 is too large. But I can scale the graph myself, so
that's not a big deal.

Thanks for any help,
Scott