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pow() giving wrong result

pow (see reference) is not defined for integers, but only for floating point numbers. If you call pow with int as an argument the result will be a double.

You can in general not assume that the result of pow will be exactly the same as if you would use pure integer math as in the function pow_longlong.

Citation from wikipedia about double precision floating point numbers:

Between 2^52=4,503,599,627,370,496 and 2^53=9,007,199,254,740,992 the representable numbers are exactly the integers. For the next range, from 2^53 to 2^54, everything is multiplied by 2, so the representable numbers are the even ones, etc.

So you get inaccurate results with pow if the result would be bigger than 2^53.





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