MathGroup Archive 2008

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ValueQ and package


In a package you typically find a construct like this:

If[Not[ValueQ[Cofactor::usage]],
Cofactor::usage = "Cofactor[m, {i, j}] calculates the (i, j)th
cofactor of matrix m."
];

My question is what the benefit of this is. Why not just use:

Cofactor::usage = "Cofactor[m, {i, j}] calculates the (i, j)th
cofactor of matrix m."

Thanks
http://bobueland.com/


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