% operator underspecified

[mzuenni]

What is the intended outcome of this expression: -1 % 2? is it -1 or 1?

[meisterT]

tested it out:

$ echo 'SET(x = -1 % 2) ASSERT(x == -1) EOF' > /tmp/test.ctd && echo -n "" | ./checktestdata /tmp/test.ctd
testdata ok!

[eldering]

FYI, the internal implementation is either standard C/C++ arithmetic, which again relies on the CPU implementation, I think, or it uses libGMP when the numbers are large, but that also follows standard C/C++ implementations, IIRC.
Note that unlike Python, in C/C++ % defines the remainder, so the following is always true: n == (n/d)*d + (n%d).
See also https://stackoverflow.com/questions/11630321/why-does-c-output-negative-numbers-when-using-modulo for details.