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author | Aleš Smodiš <aless@guru.si> | 2015-08-18 16:06:19 +0200 |
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committer | Aleš Smodiš <aless@guru.si> | 2015-08-18 16:06:19 +0200 |
commit | 95e2fe57f6e4639f6ae9f1fef368829d5090dbf6 (patch) | |
tree | 462ba05eb0c4732ca1c97739548801258bf47b40 /prolog/problems/denotational_semantics/prog_8puzzle_3/en.py |
Exported all problems from the SQLite database into the new directory structure.
Diffstat (limited to 'prolog/problems/denotational_semantics/prog_8puzzle_3/en.py')
-rw-r--r-- | prolog/problems/denotational_semantics/prog_8puzzle_3/en.py | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/prolog/problems/denotational_semantics/prog_8puzzle_3/en.py b/prolog/problems/denotational_semantics/prog_8puzzle_3/en.py new file mode 100644 index 0000000..c91b9e3 --- /dev/null +++ b/prolog/problems/denotational_semantics/prog_8puzzle_3/en.py @@ -0,0 +1,19 @@ +id = 173 +name = 'prog_8puzzle/3' +slug = '8-puzzle-solving language with semantics' + +description = '''\ +<p>Write a DCG for solving 8-puzzles. The syntax for this language should be the same as in the previous exercise: 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>up</code>, <code>down</code>}, and finally <code>[end]</code>. The starting symbol should be named <code>prog_8puzzle</code>.</p> + +<p>The meaning of a word (program) in this language has the form <code>In-->Out</code>, mapping from input to output states. Each state is a (permuted) list of numbers from 0 to 8, where 0 stands for the empty square and other numbers for the corresponding tiles. The first three numbers in the list correspond to the top row of the 8-puzzle, the next three numbers to the middle row, and the last three numbers to the last row. The meaning of instructions <code>left</code>, <code>right</code>, <code>up</code> and <code>down</code> is to move the blank tile in the given direction.</p> + +<pre> + ?- prog_8puzzle([0,1,2,3,4,5,6,7,8]-->Out, [begin,down,right,end], []). + Out = [3,1,2,4,0,5,6,7,8]. +</pre> + +<p>Helper predicates (already defined):<br /> + <code>findblank(List,I)</code> returns the 1-based index <code>I</code> of the element 0 in <code>List</code><br /> + <code>swap(List,I,J,NewList)</code> creates <code>NewList</code> by swapping elements <code>I</code> and <code>J</code> in <code>List</code></p>''' + +hint = {} |