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authorAleš Smodiš <aless@guru.si>2015-08-18 16:06:19 +0200
committerAleš Smodiš <aless@guru.si>2015-08-18 16:06:19 +0200
commit95e2fe57f6e4639f6ae9f1fef368829d5090dbf6 (patch)
tree462ba05eb0c4732ca1c97739548801258bf47b40 /prolog/problems/denotational_semantics/prog_listswap_3
Exported all problems from the SQLite database into the new directory structure.
Diffstat (limited to 'prolog/problems/denotational_semantics/prog_listswap_3')
-rw-r--r--prolog/problems/denotational_semantics/prog_listswap_3/common.py24
-rw-r--r--prolog/problems/denotational_semantics/prog_listswap_3/en.py18
2 files changed, 42 insertions, 0 deletions
diff --git a/prolog/problems/denotational_semantics/prog_listswap_3/common.py b/prolog/problems/denotational_semantics/prog_listswap_3/common.py
new file mode 100644
index 0000000..110890d
--- /dev/null
+++ b/prolog/problems/denotational_semantics/prog_listswap_3/common.py
@@ -0,0 +1,24 @@
+id = 174
+group = 'denotational_semantics'
+number = 80
+visible = True
+facts = 'denotational_semantics_aux__predicates'
+
+solution = '''\
+prog_listswap(In-->Out) -->
+ [begin], instructs174((In,1)-->(Out,_)), [end].
+
+instructs174((R0,C0)-->(R,C)) -->
+ instr174((R0,C0)-->(R,C)).
+instructs174((R0,C0)-->(R,C)) -->
+ instr174((R0,C0)-->(R1,C1)),
+ instructs174((R1,C1)-->(R,C)).
+
+instr174((R0,C0)-->(R0,C)) -->
+ [left], { C0 > 1, C is C0 - 1 ; C0 =< 1, C is C0 }.
+instr174((R0,C0)-->(R0,C)) -->
+ [right], { length(R0, LenR0),
+ ( C0 < LenR0, C is C0 + 1 ; C0 >= LenR0, C is C0 ) }.
+
+instr174((R0,C0)-->(R,C0)) -->
+ [swap], {swap(R0,C0,R)}.'''
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 = {}