#### 6.67 assume and is (4.2.01)

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

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

Ask Maple why many of their programs donâ€™t accept "assume" as mandatory directive.