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<H2><A NAME="sec:2.8"><SPAN class="sec-nr">2.8</SPAN> <SPAN class="sec-title">Reuse
of top-level bindings</SPAN></A></H2>
<A NAME="sec:topvars"></A>
<P>Bindings resulting from the successful execution of a top-level goal
are asserted in a database. These values may be reused in further
top-level queries as $Var. Only the latest binding is available.
Example:
<PRE class="code">
1 ?- maplist(plus(1), "hello", X).
X = [105,102,109,109,112]
Yes
2 ?- format('~s~n', [$X]).
ifmmp
Yes
3 ?-
</PRE>
<TABLE ALIGN=center WIDTH="75%"><TR><TD>
<B>Figure 1 : </B>Reusing top-level bindings</TABLE>
<A NAME="fig:topevelvars"></A>
<P>Note that variables may be set by executing <A class="pred" href="compare.html#=/2">=/2</A>:
<PRE class="code">
6 ?- X = statistics.
X = statistics
Yes
7 ?- $X.
28.00 seconds cpu time for 183,128 inferences
4,016 atoms, 1,904 functors, 2,042 predicates, 52 modules
55,915 byte codes; 11,239 external references
Limit Allocated In use
Heap : 624,820 Bytes
Local stack : 2,048,000 8,192 404 Bytes
Global stack : 4,096,000 16,384 968 Bytes
Trail stack : 4,096,000 8,192 432 Bytes
Yes
8 ?-
</PRE>
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