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 15:05:09 -0800 Organization: A noiseless patient Spider Lines: 56 Message-ID: <86v7f9c1y2.fsf@linuxsc.com> References: <10n80sc$3soe4$1@dont-email.me> <86v7feei2e.fsf@linuxsc.com> <10o53k6$1i0ef$2@dont-email.me> <86ms0peby6.fsf@linuxsc.com> <10ockdh$3qpk6$1@dont-email.me> <10ocrjn$3qpk6$2@dont-email.me> <86zf4mapto.fsf@linuxsc.com> <10ocvrk$3qpk6$3@dont-email.me> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Injection-Date: Thu, 05 Mar 2026 23:05:12 +0000 (UTC) Injection-Info: dont-email.me; posting-host="e10200766ffc466ebfe6a0b9c1907eec"; logging-data="229228"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX19X6/fLywM8ZZLYzQG0QO4ltOrrJU//dqo=" User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/22.4 (gnu/linux) Cancel-Lock: sha1:r8bmegdRSfU1FcaokRHgl8YqE4I= sha1:I+eF0II30n3ZCBqGFqtSINvSWmw= Xref: csiph.com comp.lang.c:396802 Lew Pitcher writes: > On Thu, 05 Mar 2026 14:12:19 -0800, Tim Rentsch wrote: > >> Lew Pitcher writes: >> >>> On Thu, 05 Mar 2026 19:09:37 +0000, Lew Pitcher wrote: >>> >>>> On Mon, 02 Mar 2026 21:09:21 -0800, Tim Rentsch wrote: >>>> [snip] >>>> >>>>> The latest challenge, which I just got through doing, is to >>>>> disallow if, for, while, goto, return, and to forbid functions >>>>> and function calls except for calls to C standard library >>>>> functions. Also no math library. :) >>>> >>>> Inventive, aren't you :-) >>>> >>>> I've got a working matrix print that (I think) satisfies your >>>> requirements, but have not started on the argument processing >>>> logic yet. I may, yet again, revise my approach, as the solution >>>> I'm using is quite tedious to code. >>> >>> OK, so the "no if statements" is a bit of a bother, but not >>> insurmountable. It's just a case of switching things around. >>> And, perhaps there's a third option as well. >>> >>> As I said, the alternatives are just tedious to code. >> >> I did manage to find some tricks to make things simpler, but >> probably the most important is ?: is your friend. > > that, and switch()/case, which is a nice substitute for if () statements > with complex bodies, or if () / else statements. > >>> But, I now need to find a replacement for sqrt() that doesn't take >>> a lot of space. Back to first principles for me, then. >> >> There is an easy way to do this, if not especially elegant: start a >> counter at 0 and count it up until counter*counter >= cutoff. Then >> there is a straightword arithmetic test to see if counter is good or >> bad. > > I was playing with the Heron's method of approximation, but was > getting anomalous numbers when coded to the restrictions of the > challenge. > > I don't mind burning cycles, and might go for the straightforward > way, but I'm still thinking on it The simple counter method is what I first coded. Then I did a binary search. The binary search is kind of clunky in a "no for() or while()" environment, so I figured out a way to use Newton-Raphson iteration. A little bit tricky to get right, but after wrestling with it I managed to get a fairly nice formulation.