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Vincent Lefevre wrote:
On 2009-05-23 22:03:05 +0200, Jean-Pierre Merlet wrote:I don't agree with the use of the empty set when dividing by an interval that includes 0. For me the empty set should be reserved when the problem at hand has indeed no solution and not when the problem is not well defined.The empty set is returned for a/b only when b = [0,0], in which case there are no solutions.
Hum...Imagine that at some point of the solving process the user get the equation u*b(x,y)=a(x,y) that he want to solve in u. The user (or a symbolic software) may write u=a/b. It may happen that for some values of x,y we have b=0 and therefore according to the proposed rule the user will get the empty set for u, believing that there is no solution, while he should be notified that (all u, b=0, a=0) is also a solution, up to him to determine if such solution is possible (by checking that a=b=0 is possible) and has any interest...
JPM