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I used to think it is nice in Fortran 90 to extent the idea of array size to include zero size. Now I realize it may be not as trivial as it seems to a programmer, thanks for this discussion! Clearly it may be a very useful concept to some applications, it is also true that for many applications, an array of size zero might just not the programmer had in mind when he/she wrote the code. I would bet that in many cases, the programmer won't even think about its possible implications to their programs. I did not until this discussion. It seems to me that not all runtime library developers have realized the implication yet. It won't surprise me if some popular ready-to-use source codes for numerical algorithms turned out to be problematic with zero-sized array arguments. The basic fact is, a zero-sized array used to be an _exception_, but not any more! An application program used to crash on zero-sized arrays, may now keep going and may even give a result. (It is good or bad, depends on your applications.) For a progammer, for the least, he/she may have to add addtional lines to assert the conditions of the argument sized zeroes, if he/she happens to understand the implications and happens to know the algorithm's applicability with zero-sized arrays. I have no intention to either suggest if the language feature is right or wrong, or even to say I like it or not (I don't know). I mearly want to state a fact that I noticed only after this discussion. (Which may not have much to do with MATMUL() anymore, I am sorry!) Humm, I thought I knew Fortran 90 already! Jing -- ________________________________ _-__-_-_ _-___--- Jing Guo, [log in to unmask], (301)805-8333(o), (301)805-7960(fx) Data Assimilation Office, Code 910.3, NASA/GSFC, Greenbelt, MD 20771 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%