From a79414bcf14d17c58e040a7b8524f7bd8f7e5e03 Mon Sep 17 00:00:00 2001
From: Nat Lasseter <nat.lasseter@york.ac.uk>
Date: Mon, 22 Jan 2024 10:23:58 +0000
Subject: Migrate from gists

---
 cpc/cpc1.rb | 23 +++++++++++++++++++++++
 cpc/cpc2.rb | 25 +++++++++++++++++++++++++
 2 files changed, 48 insertions(+)
 create mode 100644 cpc/cpc1.rb
 create mode 100644 cpc/cpc2.rb

(limited to 'cpc')

diff --git a/cpc/cpc1.rb b/cpc/cpc1.rb
new file mode 100644
index 0000000..1113de0
--- /dev/null
+++ b/cpc/cpc1.rb
@@ -0,0 +1,23 @@
+codewords = []
+
+class Integer
+  def rotate_left(bits, width = bit_width)
+    bits %= width
+    (self << bits | self >> (width - bits)) & ((1 << width) - 1)
+  end
+end
+
+(2**8).times do |candidate|
+  valid_candidate_p = true
+  8.times do |bits|
+    rotated_candidate = candidate.rotate_left(bits, 8)
+    valid_candidate_p = false if codewords.include?(rotated_candidate)
+  end
+  codewords << candidate if valid_candidate_p
+end
+
+p codewords
+puts codewords.length
+
+#=> [0, 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 37, 39, 43, 45, 47, 51, 53, 55, 59, 61, 63, 85, 87, 91, 95, 111, 119, 127, 255]
+#=> 36
diff --git a/cpc/cpc2.rb b/cpc/cpc2.rb
new file mode 100644
index 0000000..54d05c6
--- /dev/null
+++ b/cpc/cpc2.rb
@@ -0,0 +1,25 @@
+BITS = 8
+
+class Integer
+  def rotate_left(bits, width = bit_width)
+    bits %= width
+    (self << bits | self >> (width - bits)) & ((1 << width) - 1)
+  end
+end
+
+candidates = (0...(2**BITS)).to_a
+
+(2**BITS).times do |candidate|
+  next if candidates[candidate].nil?
+  (1...BITS).each do |bits|
+    candidates[candidate.rotate_left(bits, BITS)] = nil
+  end
+end
+
+codewords = candidates.compact
+
+p codewords
+puts codewords.length
+
+#=> [1, 3, 5, 7, 9, 11, 13, 15, 19, 21, 23, 25, 27, 29, 31, 37, 39, 43, 45, 47, 53, 55, 59, 61, 63, 87, 91, 95, 111, 127]
+#=> 30
-- 
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