6.67 assume and is (4.2.01)

6.67.1 Arif Zaman

Here is a simple problem which assume seems to FAIL on:

> assume(x<1);assume(y<1); 
> is ((1-x)>0); 
                      true 
 
> is ((1-y)>0); 
                      true 
 
> is((1-x)*(1-y)>0); 
                      FAIL
 

6.67.2 Colin Birch (13.2.01)

In fact the behaviour is even stranger than you report:

> restart; 
> assume(x<1);assume(y<1); 
> is((1-x)*(1-y)<0); 
 
                                false 
 
> is((1-x)*(1-y)>=0); 
 
                                 FAIL
 

6.67.3 Willard, Daniel Dr (13.2.01)

Ask Maple why many of their programs don’t accept "assume" as mandatory directive.