/usr/lib/swi-prolog/doc/Manual/allsolutions.html

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<h2 id="sec:allsolutions"><a id="sec:4.30"><span class="sec-nr">4.30</span> <span class="sec-title">Finding 
all Solutions to a Goal</span></a></h2>

<a id="sec:allsolutions"></a>

<dl class="latex">
<dt class="pubdef"><span class="pred-tag">[ISO]</span><a id="findall/3"><strong>findall</strong>(<var>+Template, 
:Goal, -Bag</var>)</a></dt>
<dd class="defbody">
Create a list of the instantiations <var>Template</var> gets 
successively on backtracking over <var>Goal</var> and unify the result 
with <var>Bag</var>. Succeeds with an empty list if <var>Goal</var> has 
no solutions. <a id="idx:findall3:1195"></a><a class="pred" href="allsolutions.html#findall/3">findall/3</a> 
is equivalent to <a id="idx:bagof3:1196"></a><a class="pred" href="allsolutions.html#bagof/3">bagof/3</a> 
with all free variables bound with the existential operator (<strong><code>^</code></strong>), 
except that <a id="idx:bagof3:1197"></a><a class="pred" href="allsolutions.html#bagof/3">bagof/3</a> 
fails when <var>Goal</var> has no solutions.</dd>
<dt class="pubdef"><a id="findall/4"><strong>findall</strong>(<var>+Template, 
:Goal, -Bag, +Tail</var>)</a></dt>
<dd class="defbody">
As <a id="idx:findall3:1198"></a><a class="pred" href="allsolutions.html#findall/3">findall/3</a>, 
but returns the result as the difference list
<var>Bag</var>-<var>Tail</var>. The 3-argument version is defined as

<pre class="code">
findall(Templ, Goal, Bag) :-
        findall(Templ, Goal, Bag, [])
</pre>

</dd>
<dt class="pubdef"><span class="pred-tag">[ISO]</span><a id="bagof/3"><strong>bagof</strong>(<var>+Template, 
:Goal, -Bag</var>)</a></dt>
<dd class="defbody">
Unify <var>Bag</var> with the alternatives of <var>Template</var>. If <var>Goal</var> 
has free variables besides the one sharing with <var>Template</var>, <a id="idx:bagof3:1199"></a><a class="pred" href="allsolutions.html#bagof/3">bagof/3</a> 
will backtrack over the alternatives of these free variables, unifying
<var>Bag</var> with the corresponding alternatives of <var>Template</var>. 
The construct <code>+<var>Var</var><code>^</code><var>Goal</var></code> 
tells <a id="idx:bagof3:1200"></a><a class="pred" href="allsolutions.html#bagof/3">bagof/3</a> 
not to bind
<var>Var</var> in <var>Goal</var>. <a id="idx:bagof3:1201"></a><a class="pred" href="allsolutions.html#bagof/3">bagof/3</a> 
fails if <var>Goal</var> has no solutions.

<p>The example below illustrates <a id="idx:bagof3:1202"></a><a class="pred" href="allsolutions.html#bagof/3">bagof/3</a> 
and the <strong><code>^</code></strong> operator. The variable bindings 
are printed together on one line to save paper.

<pre class="code">
2 ?- listing(foo).
foo(a, b, c).
foo(a, b, d).
foo(b, c, e).
foo(b, c, f).
foo(c, c, g).
true.

3 ?- bagof(C, foo(A, B, C), Cs).
A = a, B = b, C = G308, Cs = [c, d] ;
A = b, B = c, C = G308, Cs = [e, f] ;
A = c, B = c, C = G308, Cs = [g].

4 ?- bagof(C, A^foo(A, B, C), Cs).
A = G324, B = b, C = G326, Cs = [c, d] ;
A = G324, B = c, C = G326, Cs = [e, f, g].

5 ?-
</pre>

</dd>
<dt class="pubdef"><span class="pred-tag">[ISO]</span><a id="setof/3"><strong>setof</strong>(<var>+Template, 
+Goal, -Set</var>)</a></dt>
<dd class="defbody">
Equivalent to <a id="idx:bagof3:1203"></a><a class="pred" href="allsolutions.html#bagof/3">bagof/3</a>, 
but sorts the result using <a id="idx:sort2:1204"></a><a class="pred" href="builtinlist.html#sort/2">sort/2</a> 
to get a sorted list of alternatives without duplicates.
</dd>
</dl>

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swi-prolog-nox 6.6.4-2ubuntu1 / usr / lib / swi-prolog / doc / Manual / allsolutions.html
