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<h1 id="sec:foreign"><a id="sec:10"><span class="sec-nr">10</span> <span class="sec-title">Foreign
Language Interface</span></a></h1>
<a id="sec:foreign"></a>
<p>SWI-Prolog offers a powerful interface to C <cite><a class="cite" href="Bibliography.html#Kernighan:78">Kernighan &
Ritchie, 1978</a></cite>. The main design objectives of the foreign
language interface are flexibility and performance. A foreign predicate
is a C function that has the same number of arguments as the predicate
represented. C functions are provided to analyse the passed terms,
convert them to basic C types as well as to instantiate arguments using
unification. Non-deterministic foreign predicates are supported,
providing the foreign function with a handle to control backtracking.
<p>C can call Prolog predicates, providing both a query interface and an
interface to extract multiple solutions from a non-deterministic Prolog
predicate. There is no limit to the nesting of Prolog calling C, calling
Prolog, etc. It is also possible to write the `main' in C and use Prolog
as an embedded logical engine.
<p>
<hr>
<div style="text-align:center">
<h2>Section Index</h2>
</div>
<hr>
<div class="toc">
<div class="toc-h2"><a class="sec" href="foreignoverview.html"><span class="sec-nr">10.1</span> <span class="sec-title">Overview
of the Interface</span></a></div>
<div class="toc-h2"><a class="sec" href="foreignlink.html"><span class="sec-nr">10.2</span> <span class="sec-title">Linking
Foreign Modules</span></a></div>
<div class="toc-h3"><a class="sec" href="foreignlink.html#sec:10.2.1"><span class="sec-nr">10.2.1</span> <span class="sec-title">What
linking is provided?</span></a></div>
<div class="toc-h3"><a class="sec" href="foreignlink.html#sec:10.2.2"><span class="sec-nr">10.2.2</span> <span class="sec-title">What
kind of loading should I be using?</span></a></div>
<div class="toc-h3"><a class="sec" href="foreignlink.html#sec:10.2.3"><span class="sec-nr">10.2.3</span> <span class="sec-title">library(shlib):
Utility library for loading foreign objects (DLLs, shared objects)</span></a></div>
<div class="toc-h3"><a class="sec" href="foreignlink.html#sec:10.2.4"><span class="sec-nr">10.2.4</span> <span class="sec-title">Low-level
operations on shared libraries</span></a></div>
<div class="toc-h3"><a class="sec" href="foreignlink.html#sec:10.2.5"><span class="sec-nr">10.2.5</span> <span class="sec-title">Static
Linking</span></a></div>
<div class="toc-h2"><a class="sec" href="foreigntypes.html"><span class="sec-nr">10.3</span> <span class="sec-title">Interface
Data Types</span></a></div>
<div class="toc-h3"><a class="sec" href="foreigntypes.html#sec:10.3.1"><span class="sec-nr">10.3.1</span> <span class="sec-title">Type <code>term_t</code>:
a reference to a Prolog term</span></a></div>
<div class="toc-h4"><a class="sec" href="foreigntypes.html#sec:10.3.1.1"><span class="sec-nr">10.3.1.1</span> <span class="sec-title">Interaction
with the garbage collector and stack-shifter</span></a></div>
<div class="toc-h3"><a class="sec" href="foreigntypes.html#sec:10.3.2"><span class="sec-nr">10.3.2</span> <span class="sec-title">Other
foreign interface types</span></a></div>
<div class="toc-h2"><a class="sec" href="foreigninclude.html"><span class="sec-nr">10.4</span> <span class="sec-title">The
Foreign Include File</span></a></div>
<div class="toc-h3"><a class="sec" href="foreigninclude.html#sec:10.4.1"><span class="sec-nr">10.4.1</span> <span class="sec-title">Argument
Passing and Control</span></a></div>
<div class="toc-h4"><a class="sec" href="foreigninclude.html#sec:10.4.1.1"><span class="sec-nr">10.4.1.1</span> <span class="sec-title">Non-deterministic
Foreign Predicates</span></a></div>
<div class="toc-h3"><a class="sec" href="foreigninclude.html#sec:10.4.2"><span class="sec-nr">10.4.2</span> <span class="sec-title">Atoms
and functors</span></a></div>
<div class="toc-h4"><a class="sec" href="foreigninclude.html#sec:10.4.2.1"><span class="sec-nr">10.4.2.1</span> <span class="sec-title">Atoms
and atom garbage collection</span></a></div>
<div class="toc-h3"><a class="sec" href="foreigninclude.html#sec:10.4.3"><span class="sec-nr">10.4.3</span> <span class="sec-title">Analysing
Terms via the Foreign Interface</span></a></div>
<div class="toc-h4"><a class="sec" href="foreigninclude.html#sec:10.4.3.1"><span class="sec-nr">10.4.3.1</span> <span class="sec-title">Testing
the type of a term</span></a></div>
<div class="toc-h4"><a class="sec" href="foreigninclude.html#sec:10.4.3.2"><span class="sec-nr">10.4.3.2</span> <span class="sec-title">Reading
data from a term</span></a></div>
<div class="toc-h4"><a class="sec" href="foreigninclude.html#sec:10.4.3.3"><span class="sec-nr">10.4.3.3</span> <span class="sec-title">Exchanging
text using length and string</span></a></div>
<div class="toc-h4"><a class="sec" href="foreigninclude.html#sec:10.4.3.4"><span class="sec-nr">10.4.3.4</span> <span class="sec-title">Wide-character
versions</span></a></div>
<div class="toc-h4"><a class="sec" href="foreigninclude.html#sec:10.4.3.5"><span class="sec-nr">10.4.3.5</span> <span class="sec-title">Reading
a list</span></a></div>
<div class="toc-h4"><a class="sec" href="foreigninclude.html#sec:10.4.3.6"><span class="sec-nr">10.4.3.6</span> <span class="sec-title">An
example: defining write/1 in C</span></a></div>
<div class="toc-h3"><a class="sec" href="foreigninclude.html#sec:10.4.4"><span class="sec-nr">10.4.4</span> <span class="sec-title">Constructing
Terms</span></a></div>
<div class="toc-h3"><a class="sec" href="foreigninclude.html#sec:10.4.5"><span class="sec-nr">10.4.5</span> <span class="sec-title">Unifying
data</span></a></div>
<div class="toc-h3"><a class="sec" href="foreigninclude.html#sec:10.4.6"><span class="sec-nr">10.4.6</span> <span class="sec-title">Convenient
functions to generate Prolog exceptions</span></a></div>
<div class="toc-h3"><a class="sec" href="foreigninclude.html#sec:10.4.7"><span class="sec-nr">10.4.7</span> <span class="sec-title">BLOBS:
Using atoms to store arbitrary binary data</span></a></div>
<div class="toc-h4"><a class="sec" href="foreigninclude.html#sec:10.4.7.1"><span class="sec-nr">10.4.7.1</span> <span class="sec-title">Defining
a BLOB type</span></a></div>
<div class="toc-h4"><a class="sec" href="foreigninclude.html#sec:10.4.7.2"><span class="sec-nr">10.4.7.2</span> <span class="sec-title">Accessing
blobs</span></a></div>
<div class="toc-h3"><a class="sec" href="foreigninclude.html#sec:10.4.8"><span class="sec-nr">10.4.8</span> <span class="sec-title">Exchanging
GMP numbers</span></a></div>
<div class="toc-h3"><a class="sec" href="foreigninclude.html#sec:10.4.9"><span class="sec-nr">10.4.9</span> <span class="sec-title">Calling
Prolog from C</span></a></div>
<div class="toc-h4"><a class="sec" href="foreigninclude.html#sec:10.4.9.1"><span class="sec-nr">10.4.9.1</span> <span class="sec-title">Predicate
references</span></a></div>
<div class="toc-h4"><a class="sec" href="foreigninclude.html#sec:10.4.9.2"><span class="sec-nr">10.4.9.2</span> <span class="sec-title">Initiating
a query from C</span></a></div>
<div class="toc-h3"><a class="sec" href="foreigninclude.html#sec:10.4.10"><span class="sec-nr">10.4.10</span> <span class="sec-title">Discarding
Data</span></a></div>
<div class="toc-h3"><a class="sec" href="foreigninclude.html#sec:10.4.11"><span class="sec-nr">10.4.11</span> <span class="sec-title">Foreign
Code and Modules</span></a></div>
<div class="toc-h3"><a class="sec" href="foreigninclude.html#sec:10.4.12"><span class="sec-nr">10.4.12</span> <span class="sec-title">Prolog
exceptions in foreign code</span></a></div>
<div class="toc-h3"><a class="sec" href="foreigninclude.html#sec:10.4.13"><span class="sec-nr">10.4.13</span> <span class="sec-title">Catching
Signals (Software Interrupts)</span></a></div>
<div class="toc-h3"><a class="sec" href="foreigninclude.html#sec:10.4.14"><span class="sec-nr">10.4.14</span> <span class="sec-title">Miscellaneous</span></a></div>
<div class="toc-h4"><a class="sec" href="foreigninclude.html#sec:10.4.14.1"><span class="sec-nr">10.4.14.1</span> <span class="sec-title">Term
Comparison</span></a></div>
<div class="toc-h4"><a class="sec" href="foreigninclude.html#sec:10.4.14.2"><span class="sec-nr">10.4.14.2</span> <span class="sec-title">Recorded
database</span></a></div>
<div class="toc-h4"><a class="sec" href="foreigninclude.html#sec:10.4.14.3"><span class="sec-nr">10.4.14.3</span> <span class="sec-title">Getting
file names</span></a></div>
<div class="toc-h4"><a class="sec" href="foreigninclude.html#sec:10.4.14.4"><span class="sec-nr">10.4.14.4</span> <span class="sec-title">Dealing
with Prolog flags from C</span></a></div>
<div class="toc-h3"><a class="sec" href="foreigninclude.html#sec:10.4.15"><span class="sec-nr">10.4.15</span> <span class="sec-title">Errors
and warnings</span></a></div>
<div class="toc-h3"><a class="sec" href="foreigninclude.html#sec:10.4.16"><span class="sec-nr">10.4.16</span> <span class="sec-title">Environment
Control from Foreign Code</span></a></div>
<div class="toc-h3"><a class="sec" href="foreigninclude.html#sec:10.4.17"><span class="sec-nr">10.4.17</span> <span class="sec-title">Querying
Prolog</span></a></div>
<div class="toc-h3"><a class="sec" href="foreigninclude.html#sec:10.4.18"><span class="sec-nr">10.4.18</span> <span class="sec-title">Registering
Foreign Predicates</span></a></div>
<div class="toc-h3"><a class="sec" href="foreigninclude.html#sec:10.4.19"><span class="sec-nr">10.4.19</span> <span class="sec-title">Foreign
Code Hooks</span></a></div>
<div class="toc-h3"><a class="sec" href="foreigninclude.html#sec:10.4.20"><span class="sec-nr">10.4.20</span> <span class="sec-title">Storing
foreign data</span></a></div>
<div class="toc-h4"><a class="sec" href="foreigninclude.html#sec:10.4.20.1"><span class="sec-nr">10.4.20.1</span> <span class="sec-title">Examples
for storing foreign data</span></a></div>
<div class="toc-h3"><a class="sec" href="foreigninclude.html#sec:10.4.21"><span class="sec-nr">10.4.21</span> <span class="sec-title">Embedding
SWI-Prolog in other applications</span></a></div>
<div class="toc-h4"><a class="sec" href="foreigninclude.html#sec:10.4.21.1"><span class="sec-nr">10.4.21.1</span> <span class="sec-title">Threading,
Signals and embedded Prolog</span></a></div>
<div class="toc-h2"><a class="sec" href="plld.html"><span class="sec-nr">10.5</span> <span class="sec-title">Linking
embedded applications using swipl-ld</span></a></div>
<div class="toc-h3"><a class="sec" href="plld.html#sec:10.5.1"><span class="sec-nr">10.5.1</span> <span class="sec-title">A
simple example</span></a></div>
<div class="toc-h2"><a class="sec" href="findhome.html"><span class="sec-nr">10.6</span> <span class="sec-title">The
Prolog `home' directory</span></a></div>
<div class="toc-h2"><a class="sec" href="foreignxmp.html"><span class="sec-nr">10.7</span> <span class="sec-title">Example
of Using the Foreign Interface</span></a></div>
<div class="toc-h2"><a class="sec" href="foreignnotes.html"><span class="sec-nr">10.8</span> <span class="sec-title">Notes
on Using Foreign Code</span></a></div>
<div class="toc-h3"><a class="sec" href="foreignnotes.html#sec:10.8.1"><span class="sec-nr">10.8.1</span> <span class="sec-title">Memory
Allocation</span></a></div>
<div class="toc-h4"><a class="sec" href="foreignnotes.html#sec:10.8.1.1"><span class="sec-nr">10.8.1.1</span> <span class="sec-title">Boehm-GC
support</span></a></div>
<div class="toc-h3"><a class="sec" href="foreignnotes.html#sec:10.8.2"><span class="sec-nr">10.8.2</span> <span class="sec-title">Compatibility
between Prolog versions</span></a></div>
<div class="toc-h3"><a class="sec" href="foreignnotes.html#sec:10.8.3"><span class="sec-nr">10.8.3</span> <span class="sec-title">Debugging
and profiling foreign code (valgrind)</span></a></div>
<div class="toc-h3"><a class="sec" href="foreignnotes.html#sec:10.8.4"><span class="sec-nr">10.8.4</span> <span class="sec-title">Name
Conflicts in C modules</span></a></div>
<div class="toc-h3"><a class="sec" href="foreignnotes.html#sec:10.8.5"><span class="sec-nr">10.8.5</span> <span class="sec-title">Compatibility
of the Foreign Interface</span></a></div>
</div>
</body></html>
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