From 92bb2921133ee464db53b20415f8d10a0bcc7bf1 Mon Sep 17 00:00:00 2001
From: Michele Zenoni <michelezenoni1@gmail.com>
Date: Fri, 17 Sep 2021 02:24:28 +0200
Subject: [PATCH] examples: add Rule 110 example (#11516)

---
 examples/rule110.v | 100 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 100 insertions(+)
 create mode 100644 examples/rule110.v

diff --git a/examples/rule110.v b/examples/rule110.v
new file mode 100644
index 0000000000..10e439fee9
--- /dev/null
+++ b/examples/rule110.v
@@ -0,0 +1,100 @@
+import os
+import rand
+
+fn main() {
+	mut arg := '31'
+	if os.args.len != 2 {
+		println('Usage: rule110 [<n>]')
+		println('Using default `n` value: 31')
+	} else {
+		arg = os.args[1]
+	}
+
+	mut n := arg.int()
+	if n > 200 || n < 3 {
+		eprintln('`n` must be between 3 and 200!')
+		exit(1)
+	}
+
+	print('\n')
+	title := ' Rule 110 V Implementation '
+	title_len := title.len
+	if n > title_len {
+		for _ in 0 .. (n - title_len) / 2 {
+			print('=')
+		}
+		print(title)
+		for _ in 0 .. (n - title_len) / 2 {
+			print('=')
+		}
+	} else {
+		println(title[1..(title_len - 1)])
+	}
+
+	mut generation_bin := []int{len: n}
+	for i in 0 .. n {
+		generation_bin[i] = rand.intn(2)
+	}
+	print('\n')
+
+	// println('Random generated first automaton content: $generation_bin')
+	for _ in 0 .. n {
+		print_generation(generation_bin)
+		next_generation(mut generation_bin)
+	}
+}
+
+fn print_generation(arr []int) {
+	symbols := [' ', '*']!
+	for i in 0 .. arr.len {
+		print(symbols[arr[i]])
+	}
+	print('\n')
+}
+
+fn next_generation(mut gen []int) {
+	mut arr := gen.clone()
+	mut prev := 0
+	mut curr := 0
+	mut next := 0
+	for i in 0 .. arr.len {
+		if (i - 1) % gen.len < 0 {
+			prev = gen[gen.len - 1]
+		} else {
+			prev = gen[(i - 1) % gen.len]
+		}
+		curr = gen[i]
+		next = gen[(i + 1) % gen.len]
+
+		if prev == 1 {
+			if curr == 1 {
+				if next == 1 { // 111
+					arr[i] = 0
+				} else { // 110
+					arr[i] = 1
+				}
+			} else {
+				if next == 1 { // 101
+					arr[i] = 1
+				} else { // 100
+					arr[i] = 0
+				}
+			}
+		} else {
+			if curr == 1 {
+				if next == 1 { // 011
+					arr[i] = 1
+				} else { // 010
+					arr[i] = 1
+				}
+			} else {
+				if next == 1 { // 001
+					arr[i] = 1
+				} else { // 000
+					arr[i] = 0
+				}
+			}
+		}
+	}
+	gen = arr.clone()
+}