docs
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Vitor Santos Costa
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YAP Built-ins {#builtins}
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=================
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This chapter describes the core predicates that control the execution of
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Prolog programs, provide fundamental functionality such as termm manipulation or arithmetic, and support interaction with external
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resources, Many of the predicates described here have been standardised by the ISO. The standartised subset of Proloh also known as ISO-Prolog.
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In the description of the arguments of functors the following notation
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will be used:
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+ a preceding plus sign will denote an argument as an "input
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argument" - it cannot be a free variable at the time of the call;
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+ a preceding minus sign will denote an "output argument";
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+ an argument with no preceding symbol can be used in both ways.
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+ @ref YAPControl
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+ @ref Arithmetic
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+ @ref YAPChars
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+ @ref YAP_Terms
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+ @ref InputOutput
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+ @ref AbsoluteFileName
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+ @ref YAPOS
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+ @ref Internal_Database
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+ @ref Sets
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Downloading YAP {#download}
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==============
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The latest development version of Yap-6 is yap-6.3.4 and can be
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obtained from the repositories
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<http://sourceforge.net/p/yap/yap-6.3>
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and
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<https://github.com/vscosta/yap-6.3>
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YAP-6.3.4 does not use modules. Please just use `git clone` to obtain the distribution.
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Most of these repositories are basically copies of the original
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repositories at the SWI-Prolog site. YAP-6 will work either with or
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without these packages.
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Extensions to core Prolog. {#extensions}
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=========================
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YAP includes a number of extensions over the original Prolog
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language. Next, we discuss how to use the most important ones.
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+ @ref Rational_Trees
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+ @ref AttributedVariables
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+ @ref DepthLimited
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+ @ref Tabling
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+ @ref Threads
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+ @ref Profiling
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+ @ref YAPArrays
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+ @ref Parallelism
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File diff suppressed because it is too large
Load Diff
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The YAP Library {#library}
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==============
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Library files reside in the library_directory path (set by the
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`LIBDIR` variable in the Makefile for YAP). Several files in the
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library are originally from the public-domain Edinburgh Prolog library.
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- @ref apply
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- @ref apply_macros
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- @ref arg
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- @ref Association_Lists
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- @ref avl
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- @ref bhash
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- @ref block_diagram
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- @ref c_alarms
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- @ref charsio
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- @ref clauses
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- @ref cleanup
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- @ref dbqueues
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- @ref dbusage
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- @ref dgraphs
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- @ref exo_interval
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- @ref flags
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- @ref gensym
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- @ref yap_hacks
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- @ref heaps
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- @ref lam_mpi
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- @ref line_utils
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- @ref swi_listing
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- @ref lists
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- @ref mapargs
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- @ref maplist
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- @ref matlab
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- @ref matrix
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- @ref nb
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- @ref Ordered_Sets
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- @ref parameters
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- @ref queues
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- @ref random
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- @ref Pseudo_Random
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- @ref rbtrees
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- @ref regexp
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- @ref rltrees
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- @ref Splay_Trees
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- @ref operating_system_support,
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- @ref Terms
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- @ref timeout
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- @ref trees
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- @ref tries
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- @ref ugraphs
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- @ref undgraphs
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- @ref varnumbers
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- @ref wdgraphs
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- @ref wdgraphs
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- @ref wdgraphs
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- @ref wgraphs
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- @ref wundgraphs
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- @ref ypp
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Loading and Oganising YAP Programs {#consult}
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===================================
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Next, we present the main predicates and directives available to load
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files and to control the Prolog environment.
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+ @subpage YAPModules
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+ @ref YAPConsulting
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+ @ref YAPSaving
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YAP packages files {#packages}
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===================
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+ @subpage real
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+ @ref BDDs
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+ @subpage gecode
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+ @subpage myddas
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+ @ref PFL/CLP(BN)
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+ @ref ProbLog1
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+ @ref Python
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+ @subpage YAPRaptor
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+ @ref YAP-LBFGS
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+ @subpage yap-udi-indexers
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Leuven packages ported from SWI-Prolog:
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+ @subpage chr
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+ @subpage clpqr
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Running YAP {#run}
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===========
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We next describe how to invoke YAP in Unix systems.
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@subsection Running_YAP_Interactively Running YAP Interactively
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@section
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Most often you will want to use YAP in interactive mode. Assuming that
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YAP is in the user's search path, the top-level can be invoked under
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Unix with the following command:
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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yap [-s n] [-h n] [-a n] [-c IP_HOST port ] [filename]
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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All the arguments and flags are optional and have the following meaning:
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+ -?
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print a short error message.
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+ -s _Size_
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allocate _Size_ KBytes for local and global stacks. The user may
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specify <tt>M</tt> bytes.
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+ -h _Size_
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allocate _Size_ KBytes for heap and auxiliary stacks
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+ -t _Size_
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allocate _Size_ KBytes for the trail stack
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+ -L _Size_
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SWI-compatible option to allocate _Size_ K bytes for local and global stacks, the local stack
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cannot be expanded. To avoid confusion with the load option, _Size_
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must immediately follow the letter `L`.
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+ -G _Size_
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SWI-compatible option to allocate _Size_ K bytes for local and global stacks; the global
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stack cannot be expanded
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+ -T _Size_
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SWI-compatible option to allocate _Size_ K bytes for the trail stack; the trail cannot be expanded.
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+ -l _YAP_FILE_
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compile the Prolog file _YAP_FILE_ before entering the top-level.
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+ -L _YAP_FILE_
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compile the Prolog file _YAP_FILE_ and then halt. This option is
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useful for implementing scripts.
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+ -g _Goal_
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run the goal _Goal_ before top-level. The goal is converted from
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an atom to a Prolog term.
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+ -z _Goal_
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run the goal _Goal_ as top-level. The goal is converted from
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an atom to a Prolog term.
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+ -b _BOOT_FILE_
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boot code is in Prolog file _BOOT_FILE_. The filename must define
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the predicate `'$live'/0`.
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+ -c <tt>IP_HOST</tt> <tt>port</tt>
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connect standard streams to host <tt>IP_HOST</tt> at port <tt>port</tt>
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+ filename
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restore state saved in the given file
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+ -f
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do not consult initial files
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+ -q
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do not print informational messages
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+ --
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separator for arguments to Prolog code. These arguments are visible
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through the unix/1 built-in predicate.
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Note that YAP will output an error message on the following conditions:
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+
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a file name was given but the file does not exist or is not a saved
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YAP state;
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+
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the necessary amount of memory could not be allocated;
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+
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the allocated memory is not enough to restore the state.
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When restoring a saved state, YAP will allocate the
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same amount of memory as that in use when the state was saved, unless a
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different amount is specified by flags in the command line. By default,
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YAP restores the file startup.yss from the current directory or from
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the YAP library.
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+
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YAP usually boots from a saved state. The saved state will use the default
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installation directory to search for the YAP binary unless you define
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the environment variable YAPBINDIR.
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+
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YAP always tries to find saved states from the current directory
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first. If it cannot it will use the environment variable YAPLIBDIR, if
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defined, or search the default library directory.
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+
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YAP will try to find library files from the YAPSHAREDIR/library
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directory.
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@section Running_Prolog_Files Running Prolog Files
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YAP can also be used to run Prolog files as scripts, at least in
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Unix-like environments. A simple example is shown next (do not forget
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that the shell comments are very important):
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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#!/usr/local/bin/yap -L --
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#
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# Hello World script file using YAP
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#
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# put a dot because of syntax errors .
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:- write('Hello World'), nl.
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The `#!` characters specify that the script should call the binary
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file YAP. Notice that many systems will require the complete path to the
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YAP binary. The `-L` flag indicates that YAP should consult the
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current file when booting and then halt. The remaining arguments are
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then passed to YAP. Note that YAP will skip the first lines if they
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start with `#` (the comment sign for Unix's shell). YAP will
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consult the file and execute any commands.
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A slightly more sophisticated example is:
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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#!/usr/bin/yap -L --
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#
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# Hello World script file using YAP
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# .
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:- initialization(main).
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main :- write('Hello World'), nl.
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The `initialization` directive tells YAP to execute the goal main
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after consulting the file. Source code is thus compiled and `main`
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executed at the end. The `.` is useful while debugging the script
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as a Prolog program: it guarantees that the syntax error will not
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propagate to the Prolog code.
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Notice that the `--` is required so that the shell passes the extra
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arguments to YAP. As an example, consider the following script
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`dump_args`:
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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#!/usr/bin/yap -L --
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#.
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main( [] ).
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main( [H|T] ) :-
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write( H ), nl,
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main( T ).
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:- unix( argv(AllArgs) ), main( AllArgs ).
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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If you this run this script with the arguments:
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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./dump_args -s 10000
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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the script will start an YAP process with stack size `10MB`, and
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the list of arguments to the process will be empty.
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Often one wants to run the script as any other program, and for this it
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is convenient to ignore arguments to YAP. This is possible by using
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`L --` as in the next version of `dump_args`:
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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#!/usr/bin/yap -L --
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main( [] ).
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main( [H|T] ) :-
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write( H ), nl,
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main( T ).
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:- unix( argv(AllArgs) ), main( AllArgs ).
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The `--` indicates the next arguments are not for YAP. Instead,
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they must be sent directly to the argv built-in. Hence, running
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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./dump_args test
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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will write `test` on the standard output.
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@ -0,0 +1,182 @@
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Compatibility with other Prolog systems {#swi_iso_c}
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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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:- 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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|
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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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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
|
||||
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
|
||||
compatibility. Setting this flag changes the following:
|
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|
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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
|
||||
not as per the ISO definition.
|
||||
|
||||
Calling `set_prolog_flag(to_chars_mode,iso)` will switch
|
||||
YAP to use the ISO definition for
|
||||
atom_chars/2 and number_chars/2.
|
||||
|
||||
+ By default, YAP allows executable goals in directives. In ISO mode
|
||||
most directives can only be called from top level (the exceptions are
|
||||
set_prolog_flag/2 and op/3).
|
||||
|
||||
+ Error checking for meta-calls under ISO Prolog mode is stricter
|
||||
than by default.
|
||||
|
||||
+ The strict_iso flag automatically enables the ISO Prolog
|
||||
standard. This feature should disable all features not present in the
|
||||
standard.
|
||||
|
||||
The following incompatibilities between YAP and the ISO standard are
|
||||
known to still exist (please check Ulrich Neumerkel's page for more details):
|
||||
|
||||
<ul>
|
||||
|
||||
<li>Currently, YAP does not handle overflow errors in integer
|
||||
operations, and handles floating-point errors only in some
|
||||
architectures. Otherwise, YAP follows IEEE arithmetic.
|
||||
|
||||
Please inform the authors on other incompatibilities that may still
|
||||
exist.
|
||||
|
|
@ -0,0 +1,564 @@
|
|||
YAP Syntax {#YAPSyntax}
|
||||
============
|
||||
|
||||
|
||||
We will describe the syntax of YAP at two levels. We first will
|
||||
describe the syntax for Prolog terms. In a second level we describe
|
||||
the tokens from which Prolog terms are
|
||||
built.
|
||||
|
||||
@defgroup Formal_Syntax Syntax of Terms
|
||||
@ingroup YAPSyntax
|
||||
|
||||
Below, we describe the syntax of YAP terms from the different
|
||||
classes of tokens defined above. The formalism used will be <em>BNF</em>,
|
||||
extended where necessary with attributes denoting integer precedence or
|
||||
operator type.
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
term ----> subterm(1200) end_of_term_marker
|
||||
|
||||
subterm(N) ----> term(M) [M <= N]
|
||||
|
||||
term(N) ----> op(N, fx) subterm(N-1)
|
||||
| op(N, fy) subterm(N)
|
||||
| subterm(N-1) op(N, xfx) subterm(N-1)
|
||||
| subterm(N-1) op(N, xfy) subterm(N)
|
||||
| subterm(N) op(N, yfx) subterm(N-1)
|
||||
| subterm(N-1) op(N, xf)
|
||||
| subterm(N) op(N, yf)
|
||||
|
||||
term(0) ----> atom '(' arguments ')'
|
||||
| '(' subterm(1200) ')'
|
||||
| '{' subterm(1200) '}'
|
||||
| list
|
||||
| string
|
||||
| number
|
||||
| atom
|
||||
| variable
|
||||
|
||||
arguments ----> subterm(999)
|
||||
| subterm(999) ',' arguments
|
||||
|
||||
list ----> '[]'
|
||||
| '[' list_expr ']'
|
||||
|
||||
list_expr ----> subterm(999)
|
||||
| subterm(999) list_tail
|
||||
|
||||
list_tail ----> ',' list_expr
|
||||
| ',..' subterm(999)
|
||||
| '|' subterm(999)
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
Notes:
|
||||
|
||||
+ \a op(N,T) denotes an atom which has been previously declared with type
|
||||
\a T and base precedence \a N.
|
||||
|
||||
+ Since ',' is itself a pre-declared operator with type \a xfy and
|
||||
precedence 1000, is \a subterm starts with a '(', \a op must be
|
||||
followed by a space to avoid ambiguity with the case of a functor
|
||||
followed by arguments, e.g.:
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
+ (a,b) [the same as '+'(','(a,b)) of arity one]
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
versus
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
+(a,b) [the same as '+'(a,b) of arity two]
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
+
|
||||
In the first rule for term(0) no blank space should exist between
|
||||
\a atom and '('.
|
||||
|
||||
+
|
||||
Each term to be read by the YAP parser must end with a single
|
||||
dot, followed by a blank (in the sense mentioned in the previous
|
||||
paragraph). When a name consisting of a single dot could be taken for
|
||||
the end of term marker, the ambiguity should be avoided by surrounding the
|
||||
dot with single quotes.
|
||||
|
||||
|
||||
|
||||
# @defgroup Tokens Prolog Tokens
|
||||
@ingroup YAPSyntax
|
||||
|
||||
Prolog tokens are grouped into the following categories:
|
||||
|
||||
## @defgroup Numbers Numbers
|
||||
@ingroup Tokens
|
||||
|
||||
Numbers can be further subdivided into integer and floating-point numbers.
|
||||
|
||||
### @defgroup Integers Integers
|
||||
@ingroup Numbers
|
||||
|
||||
Integer numbers
|
||||
are described by the following regular expression:
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
<integer> := {<digit>+<single-quote>|0{xXo}}<alpha_numeric_char>+
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
where {...} stands for optionality, \a + optional repetition (one or
|
||||
more times), \a \\\<digit\\\> denotes one of the characters 0 ... 9, \a |
|
||||
denotes or, and \a \\\<single-quote\\\> denotes the character "'". The digits
|
||||
before the \a \\\<single-quote\\\> character, when present, form the number
|
||||
basis, that can go from 0, 1 and up to 36. Letters from `A` to
|
||||
`Z` are used when the basis is larger than 10.
|
||||
|
||||
Note that if no basis is specified then base 10 is assumed. Note also
|
||||
that the last digit of an integer token can not be immediately followed
|
||||
by one of the characters 'e', 'E', or '.'.
|
||||
|
||||
Following the ISO standard, YAP also accepts directives of the
|
||||
form `0x` to represent numbers in hexadecimal base and of the form
|
||||
`0o` to represent numbers in octal base. For usefulness,
|
||||
YAP also accepts directives of the form `0X` to represent
|
||||
numbers in hexadecimal base.
|
||||
|
||||
Example:
|
||||
the following tokens all denote the same integer
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
10 2'1010 3'101 8'12 16'a 36'a 0xa 0o12
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
Numbers of the form `0'a` are used to represent character
|
||||
constants. So, the following tokens denote the same integer:
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
0'd 100
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
YAP (version 6.3.4) supports integers that can fit
|
||||
the word size of the machine. This is 32 bits in most current machines,
|
||||
but 64 in some others, such as the Alpha running Linux or Digital
|
||||
Unix. The scanner will read larger or smaller integers erroneously.
|
||||
|
||||
### @defgroup Floats Floats
|
||||
@ingroup Numbers
|
||||
|
||||
Floating-point numbers are described by:
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
<float> := <digit>+{<dot><digit>+}
|
||||
<exponent-marker>{<sign>}<digit>+
|
||||
|<digit>+<dot><digit>+
|
||||
{<exponent-marker>{<sign>}<digit>+}
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
where \a \\\<dot\\\> denotes the decimal-point character '.',
|
||||
\a \\\<exponent-marker\\\> denotes one of 'e' or 'E', and \a \\\<sign\\\> denotes
|
||||
one of '+' or '-'.
|
||||
|
||||
Examples:
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
10.0 10e3 10e-3 3.1415e+3
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
Floating-point numbers are represented as a double in the target
|
||||
machine. This is usually a 64-bit number.
|
||||
|
||||
## Strings @defgroup Strings Character Strings
|
||||
|
||||
Strings are described by the following rules:
|
||||
|
||||
~~~~
|
||||
string --> " string_quoted_characters "
|
||||
string --> ` string_quoted_characters `
|
||||
|
||||
string_quoted_characters --> '"' '"' string_quoted_characters
|
||||
string_quoted_characters --> '\'
|
||||
escape_sequence string_quoted_characters
|
||||
string_quoted_characters -->
|
||||
string_character string_quoted_characters
|
||||
|
||||
escape_sequence --> 'a' | 'b' | 'r' | 'f' | 't' | 'n' | 'v'
|
||||
escape_sequence --> '\' | '"' | ''' | '`'
|
||||
escape_sequence --> at_most_3_octal_digit_seq_char '\'
|
||||
escape_sequence --> 'x' at_most_2_hexa_digit_seq_char '\'
|
||||
~~~~
|
||||
|
||||
where `string_character` is any character except the double quote (back quote)
|
||||
and escape characters.
|
||||
|
||||
YAP supports four different textual elements:
|
||||
|
||||
+ Atoms, mentioned above, are textual representations of symbols, that are interned in the
|
||||
data-base. They are stored either in ISO-LATIN-1 (first 256 code points), or as UTF-32.
|
||||
|
||||
+ Strings are atomic representations of text. The back-quote character is used to identify these objects in the program. Strings exist as stack objects, in the same way as other Prolog terms. As Prolog unification cannot be used to manipulate strings, YAP includes built-ins such as string_arg/3, sub_string/5, or string_concat to manipulate them efficiently. Strings are stored as opaque objects containing a
|
||||
|
||||
+ Lists of codes represent text as a list of numbers, where each number is a character code. A string of _N_ bytes requires _N_ pairs, that is _2N_ cells, leading to a total of 16 bytes per character on 64 byte machines. Thus, they are a very expensive, but very flexible representation, as one can use unification to construct and access string elements.
|
||||
|
||||
+ Lists of atoms represent text as a list of atoms, where each number has a single character code. A string of _N_ bytes also requires _2N_ pairs. They have similar properties to lists of codes.
|
||||
|
||||
The flags `double_quotes` and `backquoted_string` change the interpretation of text strings, they can take the
|
||||
values `atom`, `string`, `codes`, and `chars`.
|
||||
|
||||
Examples:
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
"" "a string" "a double-quote:"""
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
The first string is an empty string, the last string shows the use of
|
||||
double-quoting.
|
||||
|
||||
Escape sequences can be used to include the non-printable characters
|
||||
`a` (alert), `b` (backspace), `r` (carriage return),
|
||||
`f` (form feed), `t` (horizontal tabulation), `n` (new
|
||||
line), and `v` (vertical tabulation). Escape sequences also be
|
||||
include the meta-characters `\\`, `"`, `'`, and
|
||||
```. Last, one can use escape sequences to include the characters
|
||||
either as an octal or hexadecimal number.
|
||||
|
||||
The next examples demonstrates the use of escape sequences in YAP:
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
"\x0c\" "\01\" "\f" "\\"
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
The first three examples return a list including only character 12 (form
|
||||
feed). The last example escapes the escape character.
|
||||
|
||||
Escape sequences were not available in C-Prolog and in original
|
||||
versions of YAP up to 4.2.0. Escape sequences can be disabled by using:
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
:- yap_flag(character_escapes,false).
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
## @addgroup Atoms Atoms
|
||||
@ingroup Tokens
|
||||
|
||||
Atoms are defined by one of the following rules:
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
atom --> solo-character
|
||||
atom --> lower-case-letter name-character*
|
||||
atom --> symbol-character+
|
||||
atom --> single-quote single-quote
|
||||
atom --> ''' atom_quoted_characters '''
|
||||
|
||||
atom_quoted_characters --> ''' ''' atom_quoted_characters
|
||||
atom_quoted_characters --> '\' atom_sequence string_quoted_characters
|
||||
atom_quoted_characters --> character string_quoted_characters
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
where:
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
<solo-character> denotes one of: ! ;
|
||||
<symbol-character> denotes one of: # & * + - . / : <
|
||||
= > ? @ \ ^ ~ `
|
||||
<lower-case-letter> denotes one of: a...z
|
||||
<name-character> denotes one of: _ a...z A...Z 0....9
|
||||
<single-quote> denotes: '
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
and `string_character` denotes any character except the double quote
|
||||
and escape characters. Note that escape sequences in strings and atoms
|
||||
follow the same rules.
|
||||
|
||||
Examples:
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
a a12x '$a' ! => '1 2'
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
Version `4.2.0` of YAP removed the previous limit of 256
|
||||
characters on an atom. Size of an atom is now only limited by the space
|
||||
available in the system.
|
||||
|
||||
## @addgroup Variables Variables
|
||||
@ingroup Tokens
|
||||
|
||||
Variables are described by:
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
<variable-starter><variable-character>+
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
where
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
<variable-starter> denotes one of: _ A...Z
|
||||
<variable-character> denotes one of: _ a...z A...Z
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
If a variable is referred only once in a term, it needs not to be named
|
||||
and one can use the character `_` to represent the variable. These
|
||||
variables are known as anonymous variables. Note that different
|
||||
occurrences of `_` on the same term represent <em>different</em>
|
||||
anonymous variables.
|
||||
|
||||
## @addgroup Punctuation_Tokens Punctuation Tokens
|
||||
@ingroup Tokens
|
||||
Punctuation tokens consist of one of the following characters:
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
( ) , [ ] { } |
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
These characters are used to group terms.
|
||||
|
||||
@subsection Layout Layout
|
||||
Any characters with ASCII code less than or equal to 32 appearing before
|
||||
a token are ignored.
|
||||
|
||||
All the text appearing in a line after the character \a % is taken to
|
||||
be a comment and ignored (including \a %). Comments can also be
|
||||
inserted by using the sequence `/\*` to start the comment and
|
||||
`\*` followed by `/` to finish it. In the presence of any sequence of comments or
|
||||
layout characters, the YAP parser behaves as if it had found a
|
||||
single blank character. The end of a file also counts as a blank
|
||||
character for this purpose.
|
||||
|
||||
## @addgroup WideChars Encoding Wide Character Support
|
||||
@ingroup YAPSyntax
|
||||
|
||||
|
||||
YAP now implements a SWI-Prolog compatible interface to wide
|
||||
characters and the Universal Character Set (UCS). The following text
|
||||
was adapted from the SWI-Prolog manual.
|
||||
|
||||
YAP now supports wide characters, characters with character
|
||||
codes above 255 that cannot be represented in a single byte.
|
||||
<em>Universal Character Set</em> (UCS) is the ISO/IEC 10646 standard
|
||||
that specifies a unique 31-bits unsigned integer for any character in
|
||||
any language. It is a superset of 16-bit Unicode, which in turn is
|
||||
a superset of ISO 8859-1 (ISO Latin-1), a superset of US-ASCII. UCS
|
||||
can handle strings holding characters from multiple languages and
|
||||
character classification (uppercase, lowercase, digit, etc.) and
|
||||
operations such as case-conversion are unambiguously defined.
|
||||
|
||||
For this reason YAP, following SWI-Prolog, has two representations for
|
||||
atoms. If the text fits in ISO Latin-1, it is represented as an array
|
||||
of 8-bit characters. Otherwise the text is represented as an array of
|
||||
wide chars, which may take 16 or 32 bits. This representational issue
|
||||
is completely transparent to the Prolog user. Users of the foreign
|
||||
language interface sometimes need to be aware of these issues though. Notice that this will likely
|
||||
change in the future, we probably will use an UTF-8 based representation.
|
||||
|
||||
Character coding comes into view when characters of strings need to be
|
||||
read from or written to file or when they have to be communicated to
|
||||
other software components using the foreign language interface. In this
|
||||
section we only deal with I/O through streams, which includes file I/O
|
||||
as well as I/O through network sockets.
|
||||
|
||||
== @addgroup Stream_Encoding Wide character encodings on streams
|
||||
@ingroup WideChars
|
||||
|
||||
The UCS standard describes all possible characters (or code points, as they include
|
||||
ideograms, ligatures, and other symbols). The current version, Unicode 8.0, allows
|
||||
code points up to 0x10FFFF, and thus allows for 1,114,112 code points. See [Unicode Charts](http://unicode.org/charts/) for the supported languages.
|
||||
|
||||
Notice that most symbols are rarely used. Encodings represent the Unicode characters in a way
|
||||
that is more suited for communication. The most popular encoding, especially in the context of the web and in the Unix/Linux/BSD/Mac communities, is
|
||||
UTF-8. UTF-8 is compact and as it uses bytes, does not have different endianesses.
|
||||
Bytes 0...127 represent simply the corresponding US-ASCII
|
||||
character, while bytes 128...255 are used for multi-byte
|
||||
encoding of characters placed higher in the UCS space.
|
||||
|
||||
Especially on
|
||||
MS-Windows and Java the 16-bit Unicode standard, represented by pairs of bytes is
|
||||
also popular. Originally, Microsoft supported a UCS-2 with 16 bits that
|
||||
could represent only up to 64k characters. This was later extended to support the full
|
||||
Unicode, we will call the latter version UTF-16. The extension uses a hole in the first 64K code points. Characters above 0xFFFF are divided into two 2-byte words, each one in that hole. There are two versions of UTF-16: big and low
|
||||
endian. By default, UTF-16 is big endian, in practice most often it is used on Intel
|
||||
hardware that is naturally little endian.
|
||||
|
||||
UTF-32, often called UCS-4, provides a natural interface where a code point is coded as
|
||||
four octets. Unfortunately, it is also more expensive, so it is not as widely used.
|
||||
|
||||
Last, other encodings are also commonly used. One such legacy encoding is ISO-LATIN-1, that
|
||||
supported latin based languages in western europe. YAP currently uses either ISO-LATIN-1 or UTF-32
|
||||
internally.
|
||||
|
||||
Prolog supports the default encoding used by the Operating System,
|
||||
Namely, YAP checks the variables LANG, LC_ALL and LC_TYPE. Say, if at boot YAP detects that the
|
||||
environment variable `LANG` ends in "UTF-8", this encoding is
|
||||
assumed. Otherwise, the default is `text` and the translation is
|
||||
left to the wide-character functions of the C-library (note that the
|
||||
Prolog native UTF-8 mode is considerably faster than the generic
|
||||
`mbrtowc()` one).
|
||||
|
||||
Prolog allows the encoding to be specified explicitly in
|
||||
load_files/2 for loading Prolog source with an alternative
|
||||
encoding, `open/4` when opening files or using `set_stream/2` on
|
||||
any open stream (not yet implemented). For Prolog source files we also
|
||||
provide the `encoding/1` directive that can be used to switch
|
||||
between encodings that are compatible to US-ASCII (`ascii`,
|
||||
`iso_latin_1`, `utf8` and many locales).
|
||||
|
||||
For
|
||||
additional information and Unicode resources, please visit the
|
||||
[unicode](http://www.unicode.org/) organization web page.
|
||||
|
||||
YAP currently defines and supports the following encodings:
|
||||
|
||||
+ `octet`
|
||||
Default encoding for <em>binary</em> streams. This causes
|
||||
the stream to be read and written fully untranslated.
|
||||
|
||||
+ `ascii` or `US_ASCII`
|
||||
7-bit encoding in 8-bit bytes. Equivalent to `iso_latin_1`,
|
||||
but generates errors and warnings on encountering values above
|
||||
127.
|
||||
|
||||
+ `iso_latin_1` or `ISO-8859-1`
|
||||
8-bit encoding supporting many western languages. This causes
|
||||
the stream to be read and written fully untranslated.
|
||||
|
||||
+ `text`
|
||||
C-library default locale encoding for text files. Files are read and
|
||||
written using the C-library functions `mbrtowc()` and
|
||||
`wcrtomb()`. This may be the same as one of the other locales,
|
||||
notably it may be the same as `iso_latin_1` for western
|
||||
languages and `utf8` in a UTF-8 context.
|
||||
|
||||
+ `utf8`, `iso_utf8`, or `UTF-8``
|
||||
Multi-byte encoding of the full Unicode 8, compatible to `ascii` .
|
||||
See above.
|
||||
|
||||
+ `unicode_be` or `UCS-2BE`
|
||||
Unicode Big Endian. Reads input in pairs of bytes, most
|
||||
significant byte first. Can only represent 16-bit characters.
|
||||
|
||||
+ `unicode_le` or `UCS-2LE`
|
||||
Unicode Little Endian. Reads input in pairs of bytes, least
|
||||
significant byte first. Can only represent 16-bit characters.
|
||||
|
||||
+ `utf16_le` or `UTF-16LE` (experimental)
|
||||
UTF-16 Little Endian. Reads input in pairs of bytes, least
|
||||
significant byte first. Can represent the full Unicode.
|
||||
|
||||
+ `utf16_le` or `UTF-16BE` (experimental)
|
||||
Unicode Big Endian. Reads input in pairs of bytes, least
|
||||
significant byte first. Can represent the full Unicode.
|
||||
|
||||
+ `utf32_le` or `UTF-32LE` (experimental)
|
||||
UTF-16 Little Endian. Reads input in pairs of bytes, least
|
||||
significant byte first. Can represent the full Unicode.
|
||||
|
||||
+ `utf32_le` or `UTF-32BE` (experimental)
|
||||
Unicode Big Endian. Reads input in pairs of bytes, least
|
||||
significant byte first. Can only represent 16-bit characters.
|
||||
|
||||
|
||||
Note that not all encodings can represent all characters. This implies
|
||||
that writing text to a stream may cause errors because the stream
|
||||
cannot represent these characters. The behaviour of a stream on these
|
||||
errors can be controlled using `open/4` or `set_stream/2` (not
|
||||
implemented). Initially the terminal stream write the characters using
|
||||
Prolog escape sequences while other streams generate an I/O exception.
|
||||
|
||||
|
||||
|
||||
=== @addgroup BOM BOM: Byte Order Mark
|
||||
@ingroup WideChars
|
||||
|
||||
From Stream Encoding, you may have got the impression that
|
||||
text-files are complicated. This section deals with a related topic,
|
||||
making live often easier for the user, but providing another worry to
|
||||
the programmer. *BOM* or <em>Byte Order Marker</em> is a technique
|
||||
for identifying Unicode text-files as well as the encoding they
|
||||
use. Please read the [W3C](https://www.w3.org/International/questions/qa-byte-order-mark.en.php]
|
||||
page for a detailed explanation of byte-order marks.
|
||||
|
||||
BOMa are necessary on multi-byte encodings, such as UTF-16 and UTF-32. There is a BOM for UTF-8, but it is rarely used.
|
||||
The BOM is handled by the open/4 predicate. By default, text-files are
|
||||
probed for the BOM when opened for reading. If a BOM is found, the
|
||||
encoding is set accordingly and the property `bom(true)` is
|
||||
available through stream_property/2. When opening a file for
|
||||
writing, writing a BOM can be requested using the option
|
||||
`bom(true)` with `open/4`. YAP will parse an UTF-8 file for a BOM only if explicitly required to do so. Do notice that YAP will write a BOM by default on UTF-16 (including UCS-2) and
|
||||
UTF-32; otherwise the default is not to write a BOM. BOMs are not avaliable for ASCII and
|
||||
ISO-LATIN-1.
|
||||
|
||||
= @addgroup Operators Summary of YAP Predefined Operators
|
||||
@ingroup YapSyntax
|
||||
|
||||
The Prolog syntax caters for operators of three main kinds:
|
||||
|
||||
+ prefix;
|
||||
+ infix;
|
||||
+ postfix.
|
||||
|
||||
|
||||
Each operator has precedence in the range 1 to 1200, and this
|
||||
precedence is used to disambiguate expressions where the structure of the
|
||||
term denoted is not made explicit using brackets. The operator of higher
|
||||
precedence is the main functor.
|
||||
|
||||
If there are two operators with the highest precedence, the ambiguity
|
||||
is solved analyzing the types of the operators. The possible infix types are:
|
||||
_xfx_, _xfy_, and _yfx_.
|
||||
|
||||
With an operator of type _xfx_ both sub-expressions must have lower
|
||||
precedence than the operator itself, unless they are bracketed (which
|
||||
assigns to them zero precedence). With an operator type _xfy_ only the
|
||||
left-hand sub-expression must have lower precedence. The opposite happens
|
||||
for _yfx_ type.
|
||||
|
||||
A prefix operator can be of type _fx_ or _fy_.
|
||||
A postfix operator can be of type _xf_ or _yf_.
|
||||
The meaning of the notation is analogous to the above.
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
a + b * c
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
means
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
a + (b * c)
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
as + and \* have the following types and precedences:
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
:-op(500,yfx,'+').
|
||||
:-op(400,yfx,'*').
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
Now defining
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
:-op(700,xfy,'++').
|
||||
:-op(700,xfx,'=:=').
|
||||
a ++ b =:= c
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
means
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
a ++ (b =:= c)
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
The following is the list of the declarations of the predefined operators:
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
:-op(1200,fx,['?-', ':-']).
|
||||
:-op(1200,xfx,[':-','-->']).
|
||||
:-op(1150,fx,[block,dynamic,mode,public,multifile,meta_predicate,
|
||||
sequential,table,initialization]).
|
||||
:-op(1100,xfy,[';','|']).
|
||||
:-op(1050,xfy,->).
|
||||
:-op(1000,xfy,',').
|
||||
:-op(999,xfy,'.').
|
||||
:-op(900,fy,['\+', not]).
|
||||
:-op(900,fx,[nospy, spy]).
|
||||
:-op(700,xfx,[@>=,@=<,@<,@>,<,=,>,=:=,=\=,\==,>=,=<,==,\=,=..,is]).
|
||||
:-op(500,yfx,['\/','/\','+','-']).
|
||||
:-op(500,fx,['+','-']).
|
||||
:-op(400,yfx,['<<','>>','//','*','/']).
|
||||
:-op(300,xfx,mod).
|
||||
:-op(200,xfy,['^','**']).
|
||||
:-op(50,xfx,same).
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
@}
|
||||
|
|
@ -0,0 +1,55 @@
|
|||
YAP 6-3.4 Manual {#mainpage}
|
||||
====================
|
||||
|
||||
This file documents the YAP Prolog System version 6.3.4, a high-performance Prolog compiler developed at LIACC, Universidade do Porto. YAP is based on David H. D. Warren's WAM (Warren Abstract Machine), with several optimizations for better performance. YAP follows the Edinburgh tradition, and is largely compatible with DEC-10 Prolog, Quintus Prolog, and originally with C-Prolog.
|
||||
|
||||
The manual is organised as follows:
|
||||
|
||||
|
||||
+ @subpage download
|
||||
|
||||
+ @subpage install
|
||||
|
||||
+ @subpage run
|
||||
|
||||
+ @subpage consult
|
||||
|
||||
+ @subpage builtins
|
||||
|
||||
+ @subpage extensions
|
||||
|
||||
+ @subpage library
|
||||
|
||||
+ @subpage packages
|
||||
|
||||
+ @subpage swi_iso_c
|
||||
|
||||
+ @subpage YAPProgramming
|
||||
|
||||
+ @subpage fli_c_cxx
|
||||
|
||||
|
||||
|
||||
|
||||
\author Vitor Santos Costa,
|
||||
\author Luís Damas,
|
||||
\author Rogério Reis
|
||||
\author Rúben Azevedo
|
||||
|
||||
|
||||
© 1989-201 L. Damas, V. Santos Costa and Universidade
|
||||
do Porto.
|
||||
Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies.
|
||||
Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one.
|
||||
Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions.
|
||||
|
||||
This manual was written by Vítor Santos Costa,
|
||||
Luís Damas, Rogério Reis, and Rúben Azevedo. The
|
||||
manual is largely based on the DECsystem-10 Prolog User's Manual by
|
||||
D.L. Bowen, L. Byrd, F. C. N. Pereira, L. M. Pereira, and
|
||||
D. H. D. Warren. We have used comments from the Edinburgh Prolog
|
||||
library written by R. O'Keefe. Documentation from many built-ins is
|
||||
originally from the SWI-Prolog manual, with the gracious authorization
|
||||
from
|
||||
Jan Wielemaker. We would also like to gratefully
|
||||
acknowledge the contributions from Ashwin Srinivasian.
|
||||
Reference in New Issue