> Your function must be self-contained, such that someone could copy-paste it into their code and not get an error. It also must not effect the environment outside it if at all possible (no #define or mutating globals). It must be as "pure" and self-contained as the language will allow.
This is an interesting restriction, actually, with respect to style. The “natural” way I would program such an algorithm certainly doesn’t adhere to this requirement.
Producing functions that are still correct, idiomatic and legible while producing minimal changes to environment or state requires a non-beginners understanding of the runtime nature of the language.
[0]: https://github.com/oliverkwebb/moonphase?tab=readme-ov-file#...
Without having actually measured, the rust impl probably runs faster than the C impl, but that's not because rust is "faster" than C. That's because I used a closure with one call to floor() for modulus in rust, whilst in C I did 2 fmod()'s to get it because the alternative would've been to make the code unreadable or add a second function/macro (although thinking about it now, undef does exist...)
For "implement simple task in many languages" you should probably think of Rosetta Code, now at https://rosettacode.miraheze.org/wiki/Rosetta_Code
some cool things stood out:
sub fixangle($a) { $a mod 360 } # raku has built-in support for Euclidean modulo
pi # raku has pi
# Solve equation of Kepler
my $e = $M;
my $delta;
repeat { # raku's repeat loop allows initialisation of delta to be folded in
$delta = $e - $eccent * sin($e) - $M;
$e -= $delta / (1 - $eccent * cos($e));
} while abs($delta) > 1e-6;A PostScript program to visualize a calendar of moon phases (skip down to "LCAL PostScript Calendar Examples" for just that). Did some nice PS prints recently for the next 10 years, adapted to fit in a frame I had laying around.
ericpruitt•8mo ago
oliverkwebb•8mo ago
January 0th makes sense because a year starts on January 1st. You count days of the year from 1 instead of from 0. So if we are going by the day of the year, day 1 of the year should be Jan1, the consequence of this being that Jan0 exists and is Dec31 of the prev year.
I originally got into this because of my status bar on i3, hacking together C code from moontool into https://github.com/oliverkwebb/moontool about a year back.
hulitu•8mo ago
That's how bugs get introduced. /s