111 lines
3.3 KiB
Plaintext
111 lines
3.3 KiB
Plaintext
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/** @page SWIhYProlog_Emulation SWI-Prolog Emulation
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This library provides a number of SWI-Prolog builtins that are not by
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default in YAP. This support is loaded with the
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`expects_dialect(swi)` command.
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*/
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*******************************
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/** @page SWIhYProlog_Global_Variables SWI Global variables
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SWI-Prolog global variables are associations between names (atoms) and
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terms. They differ in various ways from storing information using
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assert/1 or recorda/3.
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+ The value lives on the Prolog (global) stack. This implies
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that lookup time is independent from the size of the term.
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This is particulary interesting for large data structures
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such as parsed XML documents or the CHR global constraint
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store.
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They support both global assignment using nb_setval/2 and
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backtrackable assignment using b_setval/2.
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+ Only one value (which can be an arbitrary complex Prolog
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term) can be associated to a variable at a time.
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+ Their value cannot be shared among threads. Each thread
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has its own namespace and values for global variables.
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+ Currently global variables are scoped globally. We may
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consider module scoping in future versions.
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Both b_setval/2 and nb_setval/2 implicitly create a variable if the
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referenced name does not already refer to a variable.
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Global variables may be initialised from directives to make them
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available during the program lifetime, but some considerations are
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necessary for saved-states and threads. Saved-states to not store global
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variables, which implies they have to be declared with initialization/1
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to recreate them after loading the saved state. Each thread has
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its own set of global variables, starting with an empty set. Using
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`thread_inititialization/1` to define a global variable it will be
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defined, restored after reloading a saved state and created in all
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threads that are created <em>after</em> the registration.
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*/
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*******************************
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/** @page Extensions Extensions to Prolog
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YAP includes a number of extensions over the original Prolog
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language. Next, we discuss support to the most important ones.
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*/
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*******************************
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/** @page Efficiency Efficiency Considerations
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We next discuss several issues on trying to make Prolog programs run
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fast in YAP. We assume two different programming styles:
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+ Execution of <em>deterministic</em> programs often
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boils down to a recursive loop of the form:
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~~~~~
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loop(Env) :-
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do_something(Env,NewEnv),
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loop(NewEnv).
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~~~~~
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*/
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*******************************
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/** @page ChYInterface C Language interface to YAP
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YAP provides the user with three facilities for writing
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predicates in a language other than Prolog. Under Unix systems,
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most language implementations were linkable to `C`, and the first interface exported the YAP machinery to the C language. YAP also implements most of the SWI-Prolog foreign language interface.
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This gives portability with a number of SWI-Prolog packages. Last, a new C++ based interface is
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being designed to work with the swig (@url(www.swig.org}) interface compiler.
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+ The @ref c-interface YAP C-interface exports the YAP engine.
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+ The @ref swi-c-interface emulates Jan Wielemaker's SWI foreign language interface.
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+ The @ref yap-cplus-interface is desiged to interface with Object-Oriented systems.
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*/
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