Rule 110 in Odin

rule110.odin

package main

import "core:fmt"
import "core:os"
import "core:strconv"
import "core:strings"

panic_read :: proc() {
	fmt.eprintln("cannot read from stdin")
	os.exit(1)
}

rule110 :: proc(a, b, c: u8) -> u8 {
	arr := [3]u8{a, b, c}
	switch arr {
	case {'0', '0', '0'}:
		return '0'
	case {'0', '0', '1'}:
		return '1'
	case {'0', '1', '0'}:
		return '1'
	case {'0', '1', '1'}:
		return '1'
	case {'1', '0', '0'}:
		return '0'
	case {'1', '0', '1'}:
		return '1'
	case {'1', '1', '0'}:
		return '1'
	case {'1', '1', '1'}:
		return '0'
	}
	return '0'
}

apply_rule_110 :: proc(s, o: []u8) {
	s := s
	o := o
	o[0] = rule110('0', s[0], s[1])
	for c, i in s[1:(len(s)-1)] {
		o[i+1] = rule110(s[i], s[i+1], s[i+2])
	}
	o[len(s)-1] = rule110(s[len(s)-2], s[len(s)-1], '0')
	
	for c, i in o do s[i] = c
}

ensure_binary_string_or_panic :: proc(s: []u8) {
	for c in s {
		if (c != '0' && c != '1') {
			fmt.eprintln("input is not only 0 and 1")
			os.exit(1)
		}
	}
}

run_rule110 :: proc(input: []u8, times: int) {
	ensure_binary_string_or_panic(input)
	other: []u8 = make([]u8, len(input))
	defer delete(other)

	for _ in 1..=times {
		apply_rule_110(input, other)
		for c in string(input) {
			if c == '1' do fmt.print(1)
			else do fmt.print(' ')
		}
		fmt.println("")
	}
}

main :: proc() {
	buf: [256]byte
	n, err := os.read(os.stdin, buf[:])
	if err < 0 do panic_read()

	it, ok := strconv.parse_int(string(buf[:(n-1)]))
	if !ok {
		fmt.eprintln("cannot parse input as int")
		os.exit(1)
	}

	n, err = os.read(os.stdin, buf[:])
	if err < 0 do panic_read()
	
	run_rule110(buf[:(n-1)], it)
}