Every programming language that has come since has been designed to be a general purpose programming language, therefore they don't include fixed point as a first class data type.

Therefore the financial industry continues to use COBOL.

Every time someone some tries to rewrite some crusty COBOL thing in the language de jure, they'll inevitably fuck up the rounding somewhere. The financial industry has complicated rounding rules. Or better yet, the reference implementation is buggy and the new version is right, but since the answers are different it's not accepted.

DOOM's implementation of fixed-point is a good example which should work on any platform as long as sizeof(int) >= 4.

https://github.com/id-Software/DOOM/blob/master/linuxdoom-1.... https://github.com/id-Software/DOOM/blob/master/linuxdoom-1....

Addition and subtraction will work normally. Multiplication also works normally except you need to right-shift by FRAC_BITS afterwards (and probably also cast to a larger integer type beforehand to protect against overflow).

Division is somewhat difficult since integer division is not what you want to do. DOOM's solution was to cast to double, perform the division, and then convert that back to fixed-point by multiplying by 1.0 before casting back to integer. This seems like cheating since it's using floating-point as an intermediate type, but it is safe to do because 64-bit floating point can represent all 32-bit integers. As long as you're on a platform with an FPU it's probably also faster than trying to roll your own division implementation.

Fixed point classes have been proposed many times as addition to the standard library, but have yet to be voted in.

[1] see my comment elsethread about trivial problems.