[Maxima-bugs] [ maxima-Bugs-851765 ] sum mishandles assume scopes

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Bugs item #851765, was opened at 2003-11-30 17:59
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Stavros Macrakis (macrakis)
Assigned to: Nobody/Anonymous (nobody)
Summary: sum mishandles assume scopes

Initial Comment:
assume(i>=a);
   [i >= a]
facts();
   [i >= a]         so far, so good

sum(i,i,a,b)$

facts()
   []                 oops!  It removed the assumption
is(i>=a)
   MACSYMA was unable to evaluate the predicate: i >= 
a

The problem is that dosum adds the assumption 
a<=i<=b, and then removes it when it's done.  But it 
does this in the global database, not a local one.  So it 
also removes any preexisting identical assumption.  

It also ignores any inconsistent assumptions:

assume(a>i)
sum(i,i,a,b)   => no error message

This is sort of defensible on the grounds that the inner 'i' 
really isn't the same variable as the global 'i' (as though 
Maxima understood that)... except that it *is* obeying 
the global assumptions:

   assume(i<0)
   sum(abs(i),i,1,a) => -'sum(i,i,1,a)



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