Why does cout.setf(ios::fixed) change my floats to hexadecimal?

Question

I experienced this weird issue recently having to do with cout.setf(ios::fixed). Took me quite a while to track down the cause and thought I\'d ask here to learn more.

Answer 1

Because you told it to.

From setf documentation on cppreference.com:

scientific - generate floating point types using scientific notation, or hex notation if combined with fixed: see std::scientific
fixed - generate floating point types using fixed notation, or hex notation if combined with scientific: see std::fixed

So, when setting std::fixed, you need to unset std::scientific (which is what your unmasking of std::floatfield does, because std::floatfield is std::scientific|std::fixed|(std::scientific|std::fixed)|0) to avoid the hex notation.