This is METAFONT, Version 2.718281 (TeX Live 2012/Debian) (base=mf 2012.11.2)  13 NOV 2012 17:44
**aaa.mf
(aaa.mf
testfonction
! Inconsistent equation (off by -1240).
<to be read again> 
                   ;
l.10 	w=200;
            
? s
OK, entering scrollmode...
! Inconsistent equation (off by 0.33).
<to be read again> 
                   ;
l.11 	var=1.33;
               
The equation I just read contradicts what was said before.
But don't worry; continue and I'll just ignore it.

>> (x1,y1)
>> 0
! Equation cannot be performed (pair=numeric).
<to be read again> 
                   ;
l.13 	z1=0u;
            
I'm sorry, but I don't know how to make such things equal.
(See the two expressions just above the error message.)

>> (x1,y1,1,0,0,1)
! Transform components aren't all known.
<to be read again> 
                   withpen
drawdot->...rentpen_path.shifted((EXPR0)t_)withpen
                                                  .penspeck
<to be read again> 
                   ;
l.19 	drawdot z1;
                  drawdot z2; drawdot z3;
I'm unable to apply a partially specified transformation
except to a fully known pair or transform.
Proceed, and I'll omit the transformation.

>> (x2,y1,1,0,0,1)
! Transform components aren't all known.
<to be read again> 
                   withpen
drawdot->...rentpen_path.shifted((EXPR0)t_)withpen
                                                  .penspeck
<to be read again> 
                   ;
l.19 	drawdot z1; drawdot z2;
                              drawdot z3;
I'm unable to apply a partially specified transformation
except to a fully known pair or transform.
Proceed, and I'll omit the transformation.

>> (0.5x2+0.5x1,y1+1440,1,0,0,1)
! Transform components aren't all known.
<to be read again> 
                   withpen
drawdot->...rentpen_path.shifted((EXPR0)t_)withpen
                                                  .penspeck
<to be read again> 
                   ;
l.19 	drawdot z1; drawdot z2; drawdot z3;
                                         
I'm unable to apply a partially specified transformation
except to a fully known pair or transform.
Proceed, and I'll omit the transformation.

[116]
huit [104]
spirale [115]
test [116]
Letter A [65]
Letter B [66] )
Output written on aaa.2602gf (6 characters, 73748 bytes).