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[Axiom-developer] [#261 Strange matrix addition] Bug or Feature

From: Ralf Hemmecke
Subject: [Axiom-developer] [#261 Strange matrix addition] Bug or Feature
Date: Thu, 02 Feb 2006 04:00:30 -0600

I don't know whether I should consider that 
behaviour of Axiom as a bug or a feature.

If one puts
macro S d == SquareMatrix(d,Integer)
abc(): OutputForm ==
        a2: S(2) := 1
        a3: S(3) := 1
        (a2 + a3)::OutputForm
into a file aaa.input and then says
)read aaa
one gets exactly the same result of type 
SquareMatrix(2,SquareMatrix(3,Integer)) as above.
Clearly, the same code, when put into aaa.spad does not even compile via
)co aaa

The danger is the following (which is maybe not clearly demonstrated by the 
code above):
If somebody writes some prototype of a function into an .input file and later 
wants to transform the code into a .spad form, s/he cannot expect that the 
result is the same. If the code does compile the semantics is still different 
since for the .input part the interpreter might add some knowledge.

That problem is certainly known to people who have used Axiom extensively, but 
it will come as a surprise if one is relatively new to Axiom.
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