modulo question

[martin <gremagehan () web de>]

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Hello list,

I have slightly academic question about modulo. I sent this message here 
because I thing there are many of gurus which working with modulo operator.

I have tried in python and in C++ following:
            python    C++   
1%2      1           1
- -1%2     1          -1
1%-2    -1           1
- -1%-2   -1          -1

What is right?
Do you know some applications which using modulo with negative numbers?
Have you some references to definition (mathematical def. and properties) of 
modulo?

Thanks in advance,
Martin
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