Gambit scheme incorrect calculation for numbers with decimals

Question

i'm using gambit-c intepreter to evaluate scheme arithmetic operations, but it's results are bit off. for example i execute (+ 23 20.01) and it gives me 43.010000000000005, instead of 43.01.

This only occurs if i use numbers with 2 decimal points.

Is there a fix for this?

Answer 1

It has to do with how floating point calculations are done. Please read What Every Programmer Should Know About Floating-Point Arithmetic.

You are in luck! In Scheme you fix this by using exact numbers:

(+ 23 #e20.01) ; ==> 4301/100

You can make it inexact with:

(exact->inexact (+ 23 #e20.01)) ; ==> 43.01