2016-11-16 23:17:33 +00:00
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Compatibility with other Prolog systems {#swi}
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=======================================
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YAP has been designed to be as compatible as possible with other
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Prolog systems, originally with C-Prolog\cite x and SICStus
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Prolog~\cite x . More recent work on YAP has striven at making YAP
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compatible with the ISO-Prolog standard\cite x , and with Jan
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Wielemaker's SWI-Prolog\cite x .
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SWI-Prolog and YAP have collaborated at improved compatibility \cite x . This
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resulted in Prolog extensions such as the `dialect` feature. YAP
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currently supports most of the SWI-Prolog foreign interface. The following SWI
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libraries have been adapted to YAP:
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+ @ref aggregate
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+ @ref base64
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+ @ref broadcast
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+ @ref ctypes
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+ @ref date
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+ @ref prolog_debug
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+ @ref prolog_edit
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+ @ref error
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+ @ref nb_set
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+ @ref prolog_operator
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+ @ref swi_option
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+ @ref pairs
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+ @ref pio
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+ @ref predicate_options,
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+ @ref predopts
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+ @ref prolog_clause
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+ @ref prolog_colour
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+ @ref prolog_source
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+ @ref prolog_xref
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+ @ref pure_input
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+ @ref quasi_quotations
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+ @ref read_util
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+ @ref record
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+ @ref settings
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+ @ref shlib
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+ @ref thread_pool
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+ @ref url
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+ @ref utf8
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+ @ref win_menu
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+ @ref www_browser
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Note that in general SWI code may be from an earlier version than the
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one available with SWI-Prolog. SWI-Prolog are obviously not
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responsible for any incompatibilities and/or bugs in the YAP port.
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Please do refer to the SWI-Prolog home page:
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<http://www.swi-prolog.org>
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for more information on SWI-Prolog and the SWI packages.
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Compatibility with the C-Prolog interpreter {#ChYProlog}
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-------------------------------------------
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YAP was designed so that most C-Prolog programs should run under YAP
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without changes.
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The most important difference between YAP and C-Prolog is that, being
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YAP a compiler, some changes should be made if predicates such as
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assert/1, clause/1 and retract/1 are used. First
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predicates which will change during execution should be declared as
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`dynamic` by using commands like:
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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:- dynamic f/n.
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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where `f` is the predicate name and n is the arity of the
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predicate. Note that several such predicates can be declared in a
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single command:
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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:- dynamic f/2, ..., g/1.
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Primitive predicates such as `retract` apply only to dynamic
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predicates. Finally note that not all the C-Prolog primitive predicates
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are implemented in YAP. They can easily be detected using the
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`unknown` system predicate provided by YAP.
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Last, by default YAP enables character escapes in strings. You can
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disable the special interpretation for the escape character by using:
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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:- yap_flag(character_escapes,off).
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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or by using:
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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:- yap_flag(language,cprolog).
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Compatibility with the Quintus and SICStus Prolog systems
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---------------------------------------------------------
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The Quintus Prolog system was the first Prolog compiler to use Warren's
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Abstract Machine. This system was very influential in the Prolog
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community. Quintus Prolog implemented compilation into an abstract
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machine code, which was then emulated. Quintus Prolog also included
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several new built-ins, an extensive library, and in later releases a
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garbage collector. The SICStus Prolog system, developed at SICS (Swedish
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Institute of Computer Science), is an emulator based Prolog system
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largely compatible with Quintus Prolog. SICStus Prolog has evolved
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through several versions. The current version includes several
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extensions, such as an object implementation, co-routining, and
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constraints.
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Both YAP and SICStus Prolog obey the Edinburgh Syntax and are based on
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the WAM. Even so, there are major important differences:
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+ Differently from SICStus Prolog, both consulted and dynamic code in YAP
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are compiled, not interpreted. All code in YAP is compiled.
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+ The following SICStus Prolog v3 built-ins are not (currently)
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implemented in YAP (note that this is only a partial list):
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stream_interrupt/3, reinitialize/0, help/0, help/1,
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trimcore/0, and require/1.
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+ The consult/1 predicate in YAP follows C-Prolog
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semantics. That is, it adds clauses to the data base, even for
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preexisting procedures. This is different from consult/1 in
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SICStus Prolog or SWI-Prolog.
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+ This list is incomplete.
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Compatibility with the ISO Prolog standard
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------------------------------------------
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The Prolog standard was developed by ISO/IEC JTC1/SC22/WG17, the
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international standardization working group for the programming language
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Prolog. The book "Prolog: The Standard" by Deransart, Ed-Dbali and
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Cervoni gives a complete description of this standard. Development in
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YAP from YAP4.1.6 onwards have striven at making YAP
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compatible with ISO Prolog. As such:
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+ YAP now supports all of the built-ins required by the
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ISO-standard, and,
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+ Error-handling is as required by the standard.
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YAP by default is not fully ISO standard compliant. You can set the
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language flag to `iso` to obtain better
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compatibility. Setting this flag changes the following:
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+ By default, YAP implements the
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atom_chars/2 (see Testing Terms), and
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number_chars/2, (see Testing Terms),
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built-ins as per the original Quintus Prolog definition, and
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not as per the ISO definition.
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Calling `set_prolog_flag(to_chars_mode,iso)` will switch
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YAP to use the ISO definition for
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atom_chars/2 and number_chars/2.
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+ By default, YAP allows executable goals in directives. In ISO mode
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most directives can only be called from top level (the exceptions are
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set_prolog_flag/2 and op/3).
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+ Error checking for meta-calls under ISO Prolog mode is stricter
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than by default.
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+ The strict_iso flag automatically enables the ISO Prolog
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standard. This feature should disable all features not present in the
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standard.
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The following incompatibilities between YAP and the ISO standard are
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known to still exist (please check Ulrich Neumerkel's page for more details):
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<ul>
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<li>Currently, YAP does not handle overflow errors in integer
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operations, and handles floating-point errors only in some
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architectures. Otherwise, YAP follows IEEE arithmetic.
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Please inform the authors on other incompatibilities that may still
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exist.
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