Path: csiph.com!eternal-september.org!feeder.eternal-september.org!nntp.eternal-september.org!.POSTED!not-for-mail From: Tim Rentsch Newsgroups: comp.lang.c Subject: Re: .5 against 0.5f Date: Wed, 28 Oct 2026 08:01:10 -0700 Organization: A noiseless patient Spider Lines: 39 Message-ID: <86ld7hna2x.fsf@linuxsc.com> References: <11bpvs7$1e6kc$2@dont-email.me> <11bqnvh$1np7s$1@dont-email.me> <11br5td$1to7l$1@dont-email.me> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Injection-Date: Wed, 28 Oct 2026 15:01:11 +0000 (UTC) Injection-Info: dont-email.me; logging-data="2641216"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18lmQxpCTGwg/gDa4InCSz2LBLj3l29ejM="; posting-host="863330b5bd13e85d720b0575444f578b" User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/22.4 (gnu/linux) Cancel-Lock: sha1:QLGNuAD8cN8lj9wXzqDNYkadkcM= sha1:ZfbZOWwekR4MVqQNi1qNjFkcfII= sha256:EkNwLC+wVFV0C2WD08VXijnrTFrbyIpde5aEoZxsXzY= sha1:JUv0Hrh3iOun8vOHDb36PG1Iiyg= sha256:tuUhLqJBtS2pEYlyVJctd4e09BUzl+lH2gyLUPfoZBE= Xref: csiph.com comp.lang.c:403719 James Kuyper writes: > On 2026-10-27 13:45, Steven G. Kargl wrote: > >> On Tue, 27 Oct 2026 11:53:55 +0100, fir wrote: >> >>> if ai generates me some functions it puts everywhere this f at the >>> and yet it add zeros so instead of .1 i got 0.1f >>> >>> and i obviously dont like it >>> >>> i write hvever some codes when i need speed so the question is may >>> it give some difference? >>> >>> i mean .1 maybe can be treated as doube constants so mabe occupies >>> some more memory (?) or uses some casting in coplutations (?) >>> >>> i doubt it probably it makes difference but im strictly not sure >> >> The leading zero in 0.1 or 0.1f is irrelevant, but (to me) makes >> code easier to read. The difference between 0.1 and 0.1f with >> their binary representations is a another matter. > > The number 0.1 cannot be represented exactly in binary. > > The C constant "0.1" implicitly has a double value. It has "either > the nearest representable value" to exactly 0.1, "or the larger or > smaller representable value immediately adjacent to the nearest > representable value, chosen in an implementation-defined manner." > (6.5.4.3p4). Since it's double precision constant, "representable" > means "representable as a double precision number". > > 0.1f, on the other hand, is explicitly a float value. It follows > the same rules, but with "representable" meaning "can be represented > as a float". Yes, except implementations are allowed to represent floating-point constants using a greater range and precision than the nominal type would imply. So 0.1 and 0.1f could have the same value.