7.39 bug in contourplot options, Maple 7 and Maple 8 (27.5.02)

7.39.1 Dale Alspach

It appears that there is some bug in contourplot (Maple 7 linux). The combination of variable range for y, filled=true and explicit contours produces a large red triangle (side 10^14) for (x^2+y^2)^(1/4). Changing the exponent from 1/4 to 1/2 or 1/3 yields the expected plot. 1/5 and 1/6 also produce triangles.

This plots nonsense:

contourplot((x^2+y^2)^(1/4),x=-2..2,y=-(4-x^2)^(1/2)..(4-x^2)^(1/2), 
            filled=true,contours=[0,.2,.4,.6,.8,1,1.1,1.2,1.3]);
 

These plot something reasonable:

contourplot((x^2+y^2)^(1/4),x=-2..2,y=-2..2,filled=true, 
            contours=[0,.2,.4,.6,.8,1,1.1,1.2,1.3]); 
 
contourplot((x^2+y^2)^(1/2),x=-2..2,y=-(4-x^2)^(1/2)..(4-x^2)^(1/2), 
            filled=true,contours=[0,.2,.4,.6,.8,1,1.1,1.2,1.3]); 
 
contourplot((x^2+y^2)^(1/4),x=-2..2,y=-(4-x^2)^(1/2)..(4-x^2)^(1/2), 
            filled=true,contours=10);
                                                                                    
                                                                                    
 

7.39.2 Robert Israel (4.6.02)

The bug seems to be fixed in Maple 8.

I get the same bug in Maple 8 (U. Klein)