[metapost] Labels cause errors in the postscript file.

[R S Ananda Murthy]

Hello,

I am trying to learn MetaPost on Slackware 10 system. I tried the  
following example:

beginfig(30)
pair A, B, C;
A:=(0,0); B:=(1cm,0); C:=(0,1cm);
draw A--B--C--cycle;
dotlabel.llft(btex $A$ etex, A);
dotlabel.lrt(btex $B$ etex, B);
dotlabel.top(btex $C$ etex, C);
endfig;
end;

I saved this in trial.mp. Then I executed mpost trial. I got the output  
file trial.30 without any error messages. But when I try to open  
trial.30 in gv or ggv I get several Postscript error messages. If I  
remove dotlabel statements, then there are no error messages. What is  
the problem? Please help.

Thanks for your help,

Anand