From 2f43aade2ed78389b32fd48598a2bf85ca9fdd9c Mon Sep 17 00:00:00 2001
From: funemy
Date: Tue, 25 Oct 2022 02:13:02 -0700
Subject: a different z3 constraint encoding

---
 entries/funemy/z3/z4fib.sh | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)
 create mode 100755 entries/funemy/z3/z4fib.sh

diff --git a/entries/funemy/z3/z4fib.sh b/entries/funemy/z3/z4fib.sh
new file mode 100755
index 0000000..97ae59b
--- /dev/null
+++ b/entries/funemy/z3/z4fib.sh
@@ -0,0 +1,40 @@
+#!/bin/bash
+# z3 fib, but better
+
+# Instructions:
+#  1. having z3 installed and put under your $PATH
+#  2. making sure z4fib.sh is executable, by `chmod +x z3fib.sh`
+#  3. running as `./z4fib.sh [length of the fib sequence]`
+#  4. having fun :)
+
+if [ -e fib.smt2 ]
+then
+    rm -f fib.smt2
+    touch fib.smt2
+else
+    touch fib.smt2
+fi
+
+if [ "$1" -lt "0" ]; then
+  echo "Argument must be larger than 0."
+  exit 1
+fi
+
+echo "(declare-const fib (Seq Int))" >> fib.smt2
+echo "" >> fib.smt2
+echo "(assert" >> fib.smt2
+echo "  (and" >> fib.smt2
+echo "    (= (seq.len fib) $1)" >> fib.smt2
+echo "    (= (seq.nth fib 0) 0)" >> fib.smt2
+echo "    (= (seq.nth fib 1) 1)" >> fib.smt2
+echo "    (forall ((i Int))" >> fib.smt2
+echo "      (=> (and (> i 1) (< i (seq.len fib)))" >> fib.smt2
+echo "        (= (seq.nth fib i)" >> fib.smt2
+echo "          (+ (seq.nth fib (- i 1))" >> fib.smt2
+echo "            (seq.nth fib (- i 2))))))))" >> fib.smt2
+
+
+echo "(check-sat)" >> fib.smt2
+echo "(get-model)" >> fib.smt2
+
+z3 fib.smt2
-- 
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