From 7b7bf727da3250907284368b98b0083a4b4e2386 Mon Sep 17 00:00:00 2001
From: mryouse
Date: Sat, 3 Jun 2023 20:22:18 +0000
Subject: initial commit

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 p99/p06.neb | 23 +++++++++++++++++++++++
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+; P06 Find out whether a list is a palindrome.
+; A palindrome can be read forward or backward; e.g. (x a m a x).
+
+(def odd-good (list "x" "a" "m" "a" "x")) ; odd number of elements (good)
+(def odd-bad (list "x" "f" "m" "a" "x")) ; odd number of elements (bad)
+(def even-good (list "a" "b" "b" "a")) ; even number of elements (good)
+(def even-bad (list "a" "b" "b" "f")) ; even number of elements (bad)
+(def single (list "a")) ; single element
+(def empty (list))
+
+(func palindrome? (lst)  ; by convention, funcs returning :bool end with a ?
+    (if (< (length lst) 2)  ; 0 or 1 element lists are palindromic
+        #true
+        (and
+            (eq? (first lst) (last lst))  ; first element and last element are equal
+            (palindrome? (most (rest lst))))))  ; this would be clearer if slices supported negative numbers
+
+(print (->string (palindrome? odd-good)))
+(print (->string (palindrome? odd-bad)))
+(print (->string (palindrome? even-good)))
+(print (->string (palindrome? even-bad)))
+(print (->string (palindrome? single)))
+(print (->string (palindrome? empty)))
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