7.137 bug in VectorCalculus,BasisFormat (25.6.02)

7.137.1 Crystal Johnson

"with(VectorCalculus)", the vectors are displayed in "BasisFormat", which means the components are written as a linear combination of basis vectors. There is a confirmed bug with the display when the first component(s) is(are) zero, and the next component is -1. I’ll just show it:

> < 0,-1,0 >; 
the result is displayed incorrectly as e[y]. 
 
> 2*%;
 

the result is correctly displayed as (-2)e[y].

Similarly:

> < 0,0,-1 >; 
                    e[z] 
> 2*%; 
                  (-2)e[z]
 

Watch out for it in results, because it could be quite misleading. A way to work around it is to turn off the basis format option:

> BasisFormat(false);
 

Or (as I’d be more inclined to do) just do a verification on any results of the "possibly-erroneous form " <0,0,..,1,..> by multiplying by "1." before making note of the result.