bug#19025: 24.4; precision error when adding two floats

[Stefan Monnier]

tags 19025 notabug
thanks

> (message "%s" (+ 379.744 57.93))
> The above prints 437.67400000000004.

That's the difference between floating-point numbers and real or
rational numbers.

> (message "%s" (format "%f" (+ 379.744 57.93)))

You can cut the middle man: (message "%f" (+ 379.744 57.93))

But note that this prints something "incorrect":

     M-: (message "%f" (+ 379.744 57.93))
     => 437.674000.
     M-: (equal (+ 379.744 57.93) 437.674000)
     => nil

It's just that %f rounds differently.



        Stefan