How should one compare floats in OCaml?

Question

In OCaml, comparing Integer 0 with Integer 0 returns true; however, comparing Float 0. to Float 0. returns false:

# 0 == 0;;
- : bool = true
# 0. == 0.;;
- : bool = false

How does one compare floats correctly?

always compare floats against a delta, for example if (f1 - f2) < 0.0000001 — Leo, Dec 19 '14 at 20:24
you should use a relative comparison, instead of an absolute comparison generally. — nlucaroni, Dec 19 '14 at 22:00

Jeffrey Scofield · Accepted Answer · 2014-12-19T20:32:32.007

7

Don't use ==, which is a specialized "physical equality". Use = for everyday code.

# 0 = 0;;
- : bool = true
# 0.0 = 0.0;;
- : bool = true

For inequality, use <>. The != operator is for "physical inequality", which should also be avoided like the plague in everyday code.

# 0 <> 0;;
- : bool = false
# 0.0 <> 0.0;;
- : bool = false

edited Dec 19 '14 at 20:32

answered Dec 19 '14 at 20:25

Jeffrey Scofield

Thanks Jeffrey. But then how should we mitigate '!='? '# 0. != 0.;; - : bool = true # 0 != 0;; - : bool = false' – UnSat Dec 19 '14 at 20:29
1

Excellent question. Use `<>`, for the same reason. I'll update my answer. – Jeffrey Scofield Dec 19 '14 at 20:31

1 Answers1