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From: Kenichi Asai <asai@is.ocha.ac.jp>
To: caml-list@inria.fr
Subject: [Caml-list] string_of_float (0.1 +. 0.2)
Date: Wed, 15 Jun 2022 10:59:38 +0900	[thread overview]
Message-ID: <Yqk9CiraXjKDfF51@pllab.is.ocha.ac.jp> (raw)

On OCaml 4.12.0 on M1 mac, I got:

# 0.1 +. 0.2;;
- : float = 0.300000000000000044
# string_of_float (0.1 +. 0.2);;
- : string = "0.3"

Why don't I obtain "0.300000000000000044" here?

Here is some background.  I am writing an OCaml interpreter that
mimics most part of the original OCaml interpreter.  In the OCaml
interpreter, 0.1 and 0.2 are represented as

Pexp_constant (Pconst_float ("0.1", None))
Pexp_constant (Pconst_float ("0.2", None))

When I add these two numbers, I would have to execute

let a = float_of_string "0.1"
let b = float_of_string "0.2"
let c = a +. b
let d = string_of_float c

and then return

Pexp_constant (Pconst_float (d, None))

At this point, however, since d is "0.3" instead of
"0.300000000000000044" (even though c is 0.300000000000000044), I
cannot return 0.300000000000000044 as a result.  How can I mimic the
OCaml behavior?

Sincerely,

-- 
Kenichi Asai

             reply	other threads:[~2022-06-15  1:59 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-06-15  1:59 Kenichi Asai [this message]
2022-06-15  6:22 ` Andreas Rossberg
2022-06-15  7:00   ` François Pottier
2022-06-15 14:07 ` Gabriel Scherer
2022-06-15 14:25   ` Daniel Bünzli
2022-06-16  1:45     ` Kenichi Asai
2022-06-16  6:24       ` Oleg
2022-06-16  9:01         ` Andreas Rossberg
2022-06-16  9:14           ` [Caml-list] unsubscribe Jean-Denis EIDEN JEAN-DENIS

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