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: Sort of trivial code challenge - may be interesting to you anyway Date: Thu, 05 Mar 2026 13:49:49 -0800 Organization: A noiseless patient Spider Lines: 49 Message-ID: <86cy1ic5fm.fsf@linuxsc.com> References: <10n80sc$3soe4$1@dont-email.me> <10o6vat$258sq$1@raubtier-asyl.eternal-september.org> <10o7438$2737q$2@dont-email.me> <10o92e1$2r6rf$1@raubtier-asyl.eternal-september.org> <10obb37$3jler$1@dont-email.me> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Injection-Date: Thu, 05 Mar 2026 21:49:54 +0000 (UTC) Injection-Info: dont-email.me; posting-host="e10200766ffc466ebfe6a0b9c1907eec"; logging-data="177772"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX19raMaVXbNfJC3a3Y0WvoxQ1niMLV0n6tA=" User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/22.4 (gnu/linux) Cancel-Lock: sha1:tPl7t91IhlHkEuhuLCf76DLQl5g= sha1:JTuLiyca8nt9wiiI8n47yAp88mA= Xref: csiph.com comp.lang.c:396796 scott@slp53.sl.home (Scott Lurndal) writes: > DFS writes: > >> On 3/4/2026 5:44 AM, Bonita Montero wrote: >> >> int colwidth = sprintf(cw,"%d",max) + 1; > > using ciel(log10(rows*columns)) performs better than snprintf > in this application. > > > $ printf '%f\n' $(( ceil(log10( 8*8)) )) > 2.000000 Using snprintf() is more correct and also more obviously correct. #include #include int main(){ printf( " cutoff snprintf ceil(log)\n" ); printf( " ------ -------- -----------\n" ); for( signed cutoff = 0; cutoff < 12; cutoff++ ){ int a = snprintf( 0, 0, "%d", cutoff ); int b = ceil(log10(cutoff)); printf( " %6d %8d %11d\n", cutoff, a, b ); } } gives cutoff snprintf ceil(log) ------ -------- ----------- 0 1 -2147483648 1 1 0 2 1 1 3 1 1 4 1 1 5 1 1 6 1 1 7 1 1 8 1 1 9 1 1 10 2 1 11 2 2 Also the snprintf() way doesn't need -lm. :)