diff options
Diffstat (limited to 'prolog/problems/denotational_semantics/prog_listswap_3')
| -rw-r--r-- | prolog/problems/denotational_semantics/prog_listswap_3/common.py | 4 | ||||
| -rw-r--r-- | prolog/problems/denotational_semantics/prog_listswap_3/en.py | 29 |
2 files changed, 27 insertions, 6 deletions
diff --git a/prolog/problems/denotational_semantics/prog_listswap_3/common.py b/prolog/problems/denotational_semantics/prog_listswap_3/common.py index dfa7c86..3ad93e8 100644 --- a/prolog/problems/denotational_semantics/prog_listswap_3/common.py +++ b/prolog/problems/denotational_semantics/prog_listswap_3/common.py @@ -1,6 +1,6 @@ id = 174 -number = 80 -visible = False +number = 20 +visible = True facts = 'denotational_semantics_aux__predicates' solution = '''\ diff --git a/prolog/problems/denotational_semantics/prog_listswap_3/en.py b/prolog/problems/denotational_semantics/prog_listswap_3/en.py index b8e9769..e275335 100644 --- a/prolog/problems/denotational_semantics/prog_listswap_3/en.py +++ b/prolog/problems/denotational_semantics/prog_listswap_3/en.py @@ -2,16 +2,37 @@ 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> +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> +<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 /> - <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>''' +<p> +Helper predicates (already defined): +</p> +<ul> +<li><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></li> +</ul> +''' hint = {} |