From 181758e5e739b4aedf9ea1bb256d9bde09d55caf Mon Sep 17 00:00:00 2001
From: Igor Pashev <pashev.igor@gmail.com>
Date: Wed, 16 Nov 2022 20:05:15 +0200
Subject: Update Prolog

So it does not crash on empty list.
---
 gcd.pro | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/gcd.pro b/gcd.pro
index 1d888e9..793d307 100644
--- a/gcd.pro
+++ b/gcd.pro
@@ -6,8 +6,6 @@
 % # ./gcd-pro 22 33 44 121
 
 
-% 1st number, 2nd number, GCD
-
 % It is true that GCD of A and 0 is A
 % (The fact is GCD of A and 0 is A)
 gcd2(A, 0, A).
@@ -20,14 +18,18 @@ gcdn(A, [], A).
 gcdn(A, [B|Bs], G) :- gcd2(A, B, N), gcdn(N, Bs, G).
 gcdn([A|As], G) :- gcdn(A, As, G).
 
-:- initialization(main).
-
 str2int([], []).
 str2int([S|St], [N|Nt]) :- number_atom(N, S), str2int(St, Nt).
 
+not_empty([]) :- halt.
+not_empty(_).
+
 main :-
     argument_list(Args),
+    not_empty(Args),
     str2int(Args, Numbers),
     gcdn(Numbers, G),
     write(G), nl.
 
+:- initialization(main).
+
-- 
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