From 95e2fe57f6e4639f6ae9f1fef368829d5090dbf6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ale=C5=A1=20Smodi=C5=A1?= <aless@guru.si>
Date: Tue, 18 Aug 2015 16:06:19 +0200
Subject: Exported all problems from the SQLite database into the new directory
 structure.

---
 .../denotational_semantics/prog_listswap_3/en.py       | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)
 create mode 100644 prolog/problems/denotational_semantics/prog_listswap_3/en.py

(limited to 'prolog/problems/denotational_semantics/prog_listswap_3/en.py')

diff --git a/prolog/problems/denotational_semantics/prog_listswap_3/en.py b/prolog/problems/denotational_semantics/prog_listswap_3/en.py
new file mode 100644
index 0000000..1a7cb79
--- /dev/null
+++ b/prolog/problems/denotational_semantics/prog_listswap_3/en.py
@@ -0,0 +1,18 @@
+id = 174
+name = 'prog_listswap/3'
+slug = 'list-manipulation language with semantics'
+
+description = '''\
+<p>Write a DCG for manipulating list elements. The first symbol in every word is <code>[begin]</code>, followed by any sequence of "instruction" symbols from the set {<code>left</code>, <code>right</code>, <code>swap</code>}, and finally <code>[end]</code>. The starting symbol should be named <code>prog_listswap</code>.</p>
+
+<p>The meaning of a word (program) in this language has the form <code>In-->Out</code>, mapping from input to output lists. Besides the list contents, internal states also hold the current cursor position. The <code>left</code> and <code>right</code> instructions move the cursor one step in the given direction, while the <code>swap</code> instruction swaps the element under the cursor with its left neighbor (and fails if cursor is currently pointing to the first element of the list).</p>
+
+<pre>
+  ?- prog_listswap([1,2,3,4]-->Out, [begin,right,swap,end], []).
+    Out = [2,1,3,4].
+</pre>
+
+<p>Helper predicate (already defined):<br />
+&nbsp;&nbsp;<code>swap(List,I,NewList)</code> creates <code>NewList</code> by swapping the <code>I</code>th element with its left neighbor in <code>List</code></p>'''
+
+hint = {}
-- 
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