From f128e3939d1b547a3a408529b8698d08ebcaf6d7 Mon Sep 17 00:00:00 2001
From: Masaya Tojo <masaya@tojo.tokyo>
Date: Sun, 25 Jul 2021 17:54:07 +0900
Subject: consecutive-fibonacci-numbers-are-coprime: ガードを追加
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---
 consecutive-fibonacci-numbers-are-coprime.lisp | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

(limited to 'consecutive-fibonacci-numbers-are-coprime.lisp')

diff --git a/consecutive-fibonacci-numbers-are-coprime.lisp b/consecutive-fibonacci-numbers-are-coprime.lisp
index d80ce43..482eb65 100644
--- a/consecutive-fibonacci-numbers-are-coprime.lisp
+++ b/consecutive-fibonacci-numbers-are-coprime.lisp
@@ -5,6 +5,7 @@
 
 ;; フィボナッチ関数の定義
 (defun fibonacci (n)
+  (declare (xargs :guard (natp n)))
   (cond
     ((zp n) 0)
     ((equal n 1) 1)
@@ -13,7 +14,9 @@
 
 ;; ユークリッドの互除法による最大公約数の定義
 (defun gcd$ (n m)
-  (declare (xargs :measure (+ (nfix m) (nfix n))))
+  (declare (xargs :measure (+ (nfix m) (nfix n))
+                  :guard (and (posp n)
+                              (posp m))))
   (cond
     ((or (not (posp n))
          (not (posp m))
-- 
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