> > (%i1) eq:a=b$
> sin(a),eq;
> (Returns sin(b))
> sin(b),eq;
> doesn't work
The notation << xxx, yyy >>> is actually a shorthand for << ev( xxx,
yyy ) >>>. When yyy evaluates to something of the form <<< aaa=bbb
>>>, it means "evaluate xxx in an environment where aaa is bound to
the value bbb". Note that it is NOT interpreting aaa=bbb as an
equation, symmetrical in aaa and bbb.
In general, the << xxx, yyy >>> notation is very handy for many
things, but its semantics are actually quite tricky, so it is often
better to use more explicit manipulations.
-s