move big doc chunks to md files
also moe icons to docs/
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107
pl/absf.md
Normal file
@ -0,0 +1,107 @@
|
||||
|
||||
@addtogroup absolute_file_name
|
||||
|
||||
@pred absolute_file_name(+File:atom, +Options:list, +Path:atom) is nondet
|
||||
@pred absolute_file_name(-File:atom, +Path:atom, +Options:list) is nondet
|
||||
|
||||
_Options_ is a list of options to guide the conversion:
|
||||
|
||||
- extensions(+ _ListOfExtensions_)
|
||||
|
||||
List of file-name suffixes to add to try adding to the file. The
|
||||
Default is the empty suffix, `''`. For each extension,
|
||||
absolute_file_name/3 will first add the extension and then verify
|
||||
the conditions imposed by the other options. If the condition
|
||||
fails, the next extension of the list is tried. Extensions may
|
||||
be specified both with dot, as `.ext`, or without, as plain
|
||||
`ext`.
|
||||
|
||||
- relative_to(+ _FileOrDir_ )
|
||||
|
||||
Resolve the path relative to the given directory or directory the
|
||||
holding the given file. Without this option, paths are resolved
|
||||
relative to the working directory (see working_directory/2) or,
|
||||
if _Spec_ is atomic and absolute_file_name/3 is executed
|
||||
in a directive, it uses the current source-file as reference.
|
||||
|
||||
- access(+ _Mode_ )
|
||||
|
||||
Imposes the condition access_file( _File_ , _Mode_ ). _Mode_ is one of `read`, `write`, `append`, `exist` or
|
||||
`none` (default).
|
||||
|
||||
See also access_file/2.
|
||||
|
||||
- file_type(+ _Type_ )
|
||||
|
||||
Defines suffixes matching one of several pre-specified type of files. Default mapping is as follows:
|
||||
|
||||
1. `txt` implies `[ '' ]`,
|
||||
|
||||
2. `prolog` implies `['.yap', '.pl', '.prolog', '']`,
|
||||
|
||||
3. `executable` implies `['.so', ',dylib', '.dll']` depending on the Operating system,
|
||||
|
||||
4. `qly` implies `['.qly', '']`,
|
||||
|
||||
5. `directory` implies `['']`,
|
||||
|
||||
6. The file-type `source` is an alias for `prolog` designed to support compatibility with SICStus Prolog. See also prolog_file_type/2.
|
||||
|
||||
Notice that this predicate only
|
||||
returns non-directories, unless the option `file_type(directory)` is
|
||||
specified, or unless `access(none)`.
|
||||
|
||||
- file_errors(`fail`/`error`)
|
||||
|
||||
If `error` (default), throw `existence_error` exception
|
||||
if the file cannot be found. If `fail`, stay silent.
|
||||
|
||||
- solutions(`first`/`all`)
|
||||
|
||||
If `first` (default), commit to the first solution. Otherwise
|
||||
absolute_file_name will enumerate all solutions via backtracking.
|
||||
|
||||
- expand(`true`/`false`)
|
||||
|
||||
If `true` (default is `false`) and _Spec_ is atomic, call
|
||||
expand_file_name/2 followed by member/2 on _Spec_ before
|
||||
proceeding. This is originally a SWI-Prolog extension, but
|
||||
whereas SWI-Prolog implements its own conventions, YAP uses the
|
||||
shell's `glob` primitive.
|
||||
|
||||
- glob(`Pattern`)
|
||||
|
||||
If _Pattern_ is atomic, add the pattern as a suffix to the current expansion, and call
|
||||
expand_file_name/2 followed by member/2 on the result. This is originally a SICStus Prolog exception.
|
||||
|
||||
Both `glob` and `expand` rely on the same underlying
|
||||
mechanism. YAP gives preference to `glob`.
|
||||
|
||||
- verbose_file_search(`true`/`false`)
|
||||
|
||||
If `true` (default is `false`) output messages during
|
||||
search. This is often helpful when debugging. Corresponds to the
|
||||
SWI-Prolog flag `verbose_file_search` (also available in YAP).
|
||||
|
||||
|
||||
Compatibility considerations to common argument-order in ISO as well
|
||||
as SICStus absolute_file_name/3 forced us to be flexible here.
|
||||
If the last argument is a list and the second not, the arguments are
|
||||
swapped, making the call
|
||||
~~~~~~~~~~~prolog
|
||||
absolute_file_name(+ _Spec_ , - _Path_ ,+ _Options_ )
|
||||
~~~~~~~~~~~
|
||||
valid as well.
|
||||
|
||||
|
||||
@pred user:library_directory(?Directory:atom) is nondet, dynamic
|
||||
|
||||
Dynamic, multi-file predicate that succeeds when _Directory_ is a
|
||||
current library directory name. Asserted in the user module.
|
||||
|
||||
Library directories are the places where files specified in the form
|
||||
`library( _File_ )` are searched by the predicates consult/1,
|
||||
reconsult/1, use_module/1, ensure_loaded/1, and load_files/2.
|
||||
|
||||
This directory is initialized by a rule that calls the system predicate
|
||||
system_library/1.
|
@ -27,14 +27,15 @@ work with. Most packages included in YAP that use attributed
|
||||
variables, such as CHR, CLP(FD), and CLP(QR), rely on the SWI-Prolog
|
||||
interface.
|
||||
|
||||
+ @ref Old_Style_Attribute_Declarations
|
||||
+ @ref attributes
|
||||
+ @ref New_Style_Attribute_Declarations
|
||||
+ @ref CohYroutining
|
||||
+ @ref AttributeVariables_Builtins
|
||||
|
||||
@{
|
||||
|
||||
@defgroup Old_Style_Attribute_Declarations SICStus Style attribute declarations.
|
||||
@ingroup AttributeDeclarations
|
||||
@defgroup attributes SICStus Style attribute declarations.
|
||||
@ingroup AttributedVariables
|
||||
|
||||
The YAP library `atts` implements attribute variables in the style of
|
||||
SICStus Prolog. Attributed variables work as follows:
|
||||
|
337
pl/modules.md
Normal file
@ -0,0 +1,337 @@
|
||||
|
||||
@defgroup YAPModules The YAP Module system
|
||||
|
||||
@ingroup consult
|
||||
|
||||
The YAP module system is based on the Quintus/SISCtus module
|
||||
system ˜\cite quintus . In this design, modules are named collections of predicates,
|
||||
and all predicates belong to a single module. By default, predicates are only
|
||||
visible within a module, or _private_ to that module. The module
|
||||
may also define a list of predicates that are
|
||||
_exported_, that is, visible to other modules.
|
||||
|
||||
The main predicates in the module system are:
|
||||
|
||||
* module/2 associates a source file to a module. It has two arguments: the name of the new module, and a list of predicates exported by the module.
|
||||
|
||||
* use_module/1 and use_module/2 can be used to load a module. They take as first argument the source file for the module. Whereas use_module/1 loads all exported predicates, use_module/2 only takes the ones given by the second argument.
|
||||
|
||||
YAP pre-defines a number of modules. Most system predicates belong to
|
||||
the module `prolog`. Predicates from the module `prolog` are
|
||||
automatically visible to every module. The `system` module was
|
||||
introduced for SWI-Prolog compatibility, and in YAP mostly acts as an
|
||||
alias to `prolog`. The `user` module is also visible to all other modules.
|
||||
|
||||
The YAP engine is always associated to a module, the current <em>source
|
||||
module</em> or <em>type-in module</em>. By default, all predicates
|
||||
read-in and all calls to a goal will be made to predicates visible to
|
||||
the current source module, Initially, the source module for YAP is the
|
||||
module `user`. Thus Prolog programs that do not define modules will
|
||||
operate within the `user` module. In this case, all predicates will be
|
||||
visible to all source files.
|
||||
|
||||
YAP includes a number of libraries and packages, most of them
|
||||
defining their own modules. Note that there is no system mechanism to
|
||||
avoid clashes between module names, so it is up to the programmer to
|
||||
carefully choose the names for her own program modules.
|
||||
|
||||
The main mechanism to change the current type-in module is by using
|
||||
the module/2 declaration.This declaration sets the source module when
|
||||
it starts consulting a file, and resets it at the end. One can set
|
||||
the type-in module permanently by using the built-in `module/1`.
|
||||
|
||||
\subsection Explicit Naming
|
||||
|
||||
The module system allows one to _explicitly_ specify the source mode for
|
||||
a clause by prefixing a clause with its module, say:
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.prolog}
|
||||
user:(a :- b).
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
it is also possible to type
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.prolog}
|
||||
|
||||
user:a :- user:b.
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
both formulations describe the same clause, independently of the
|
||||
current type-in module.
|
||||
|
||||
In fact, it is sufficient to specify the source mode for the clause's
|
||||
head:
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.prolog}
|
||||
user:a :- b.
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
if the current type-in module is `m`, the clause could also be written as:
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.prolog}
|
||||
user:a :- m:b.
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
The compiler rewrites the source clauses to ensure that explicit calls
|
||||
are respected, and that implicit calls are made to the current source
|
||||
module.
|
||||
|
||||
A goal should refer to a predicate visible within the current type-in
|
||||
module. Thus, if a goal appears in a text file with a module
|
||||
declaration, the goal refers to that module's context (but see the
|
||||
initialization/1 directive for more details).
|
||||
|
||||
Again, one can override this rule by prefixing a goal with a module to
|
||||
be consulted. The following query:
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.prolog}
|
||||
?- nasa:launch(apollo,13).
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
invokes the goal `launch(apollo,13)` as if the current source
|
||||
module was `nasa`.
|
||||
|
||||
YAP and other Prolog systems allow the module prefix to see all
|
||||
predicates visible in the module, including predicates private to the
|
||||
module. This rule allows maximum flexibility, but it also breaks
|
||||
encapsulation and should be used with care. The ciao language proposes
|
||||
a different approach to this problem, see \cite DBLP:conf/cl/GrasH00 .
|
||||
|
||||
Modules are not always associated with a source-file. They
|
||||
may range over several files, by using the
|
||||
`include`directive. Moreover, they may not be associated to any source
|
||||
file. As an example,
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.prolog}
|
||||
?- assert( nasa:launch(apollo,13) ).
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
will create a module `nasa`, if does not already exist. In fact it is
|
||||
sufficient to call a predicate from a module to implicitly create the
|
||||
module. Hence after this call:
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.prolog}
|
||||
?- nasa:launch(apollo,13).
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
there will be a `nasa`module in the system, even if nasa:launch/2 is
|
||||
not at all defined.
|
||||
|
||||
\pred use_module( +Files ) is directive
|
||||
loads a module file
|
||||
|
||||
This predicate loads the file specified by _Files_, importing all
|
||||
their public predicates into the current type-in module. It is
|
||||
implemented as if by:
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.prolog}
|
||||
use_module(F) :-
|
||||
load_files(F, [if(not_loaded),must_be_module(true)]).
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
Notice that _Files_ may be a single file, or a list with a number
|
||||
files. The _Files_ are loaded in YAP only once, even if they have been
|
||||
updated meanwhile. YAP should also verify whether the files actually
|
||||
define modules. Please consult load_files/3 for other options when
|
||||
loading a file.
|
||||
|
||||
Predicate name clashes between two different modules may arise, either
|
||||
when trying to import predicates that are also defined in the current
|
||||
type-in module, or by trying to import the same predicate from two
|
||||
different modules.
|
||||
|
||||
In the first case, the local predicate is considered to have priority
|
||||
and use_module/1 simply gives a warning. As an example, if the file
|
||||
`a.pl` contains:
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.prolog}
|
||||
:- module( a, [a/1] ).
|
||||
|
||||
:- use_module(b).
|
||||
|
||||
a(1).
|
||||
a(X) :- b(X).
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
and the file `b.pl` contains:
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.prolog}
|
||||
:- module( b, [a/1,b/1] ).
|
||||
|
||||
a(2).
|
||||
|
||||
b(1).
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
YAP will execute as follows:
|
||||
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.prolog}
|
||||
?- [a].
|
||||
% consulting .../a.pl...
|
||||
% consulting .../b.pl...
|
||||
% consulted .../b.pl in module b, 0 msec 0 bytes
|
||||
% consulted .../a.pl in module a, 1 msec 0 bytes
|
||||
true.
|
||||
?- a(X).
|
||||
X = 1 ? ;
|
||||
X = 1.
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
The example shows that the query `a(X)`has a single answer, the one
|
||||
defined in `a.pl`. Calls to `a(X)`succeed in the top-level, because
|
||||
the module `a` was loaded into `user`. On the other hand, `b(X)`is not
|
||||
exported by `a.pl`, and is not available to calls, although it can be
|
||||
accessed as a predicate in the module 'a' by using the `:` operator.
|
||||
|
||||
Next, consider the three files `c.pl`, `d1.pl`, and `d2.pl`:
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.prolog}
|
||||
% c.pl
|
||||
:- module( c, [a/1] ).
|
||||
|
||||
:- use_module([d1, d2]).
|
||||
|
||||
a(X) :-
|
||||
b(X).
|
||||
a(X) :-
|
||||
c(X).
|
||||
a(X) :-
|
||||
d(X).
|
||||
|
||||
% d1.pl
|
||||
:- module( d1, [b/1,c/1] ).
|
||||
|
||||
b(2).
|
||||
c(3).
|
||||
|
||||
|
||||
% d2.pl
|
||||
:- module( d2, [b/1,d/1] ).
|
||||
|
||||
b(1).
|
||||
d(4).
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
The result is as follows:
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.prolog}
|
||||
./yap -l c
|
||||
YAP 6.3.4 (x86_64-darwin13.3.0): Tue Jul 15 10:42:11 CDT 2014
|
||||
|
||||
ERROR!!
|
||||
at line 3 in o/d2.pl,
|
||||
PERMISSION ERROR- loading .../c.pl: modules d1 and d2 both define b/1
|
||||
?- a(X).
|
||||
X = 2 ? ;
|
||||
ERROR!!
|
||||
EXISTENCE ERROR- procedure c/1 is undefined, called from context prolog:$user_call/2
|
||||
Goal was c:c(_131290)
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
The state of the module system after this error is undefined.
|
||||
|
||||
@\pred module(+ M:atom,+ L:list ) is directive
|
||||
the current file defines module _M_ with exports _L_. The list may include
|
||||
|
||||
+ predicate indicators
|
||||
|
||||
+ operator definitions that look like calls to op/3.
|
||||
|
||||
The list _L_ may include predicates imported from other modules. If
|
||||
you want to fully reexport a module, or a sub-set, also consider reexport/1.
|
||||
|
||||
Similar to module/2, this directive defines the file where it
|
||||
appears in as a module file; it must be the first declaration in the file.
|
||||
_M_ must be an atom specifying the module name; _L_ must be a
|
||||
list containing the module's public predicates specification, in the
|
||||
form `[predicate_name/arity,...]`.
|
||||
|
||||
The last argument _Options_ must be a list of options, which can be:
|
||||
+ <b>filename</b>
|
||||
the filename for a module to import into the current module.
|
||||
|
||||
+ <b>library( +File )</b>
|
||||
a library file to import into the current module.
|
||||
|
||||
+ <b>hide( +Opt)</b>
|
||||
if _Opt_ is `false`, keep source code for current module, if `true`, disable.
|
||||
|
||||
+ <b>export(+PredicateIndicator )</b>
|
||||
Add predicates to the public list of the context module. This implies
|
||||
the predicate will be imported into another module if this module
|
||||
is imported with use_module/1 and use_module/2.
|
||||
|
||||
+ <b>export_list(? _Mod_,? _ListOfPredicateIndicator_)</b>
|
||||
The list _ListOfPredicateIndicator_ contains all predicates
|
||||
exported by module _Mod_
|
||||
|
||||
Note that predicates are normally exported using the directive
|
||||
`module/2`. The `export/1` argumwnt is meant to allow export from
|
||||
dynamically created modules. The directive argument may also be a list
|
||||
of predicates.
|
||||
|
||||
@pred use_module(+Files, +Imports)
|
||||
loads a module file but only imports the named predicates
|
||||
|
||||
|
||||
This predicate loads the file specified by _Files_, importing their
|
||||
public predicates specified by _Imports_ into the current type-in
|
||||
module. It is implemented as if by:
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.prolog}
|
||||
use_module(Files, Imports) :-
|
||||
load_files(Files, [if(not_loaded),must_be_module(true),imports(Imports)]).
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
The _Imports_ argument may be use to specify which predicates one
|
||||
wants to load. It can also be used to give the predicates a different name. As an example,
|
||||
the graphs library is implemented on top of the red-black trees library, and some predicates are just aliases:
|
||||
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.prolog}
|
||||
:- use_module(library(rbtrees), [
|
||||
rb_min/3 as min_assoc,
|
||||
rb_max/3 as max_assoc,
|
||||
|
||||
...]).
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
Unfortunately it is still not possible to change argument order.
|
||||
|
||||
|
||||
\pred module(+ M:atom,+ L:list ) is directive
|
||||
the current file defines module _M_ with exports _L_. The list may include
|
||||
|
||||
+ predicate indicators
|
||||
|
||||
+ operator definitions that look like calls to op/3.
|
||||
|
||||
The list _L_ may include predicates imported from other modules. If
|
||||
you want to fully reexport a module, or a sub-set, also consider reexport/1.
|
||||
|
||||
Similar to module/2, this directive defines the file where it
|
||||
appears in as a module file; it must be the first declaration in the file.
|
||||
_M_ must be an atom specifying the module name; _L_ must be a
|
||||
list containing the module's public predicates specification, in the
|
||||
form `[predicate_name/arity,...]`.
|
||||
|
||||
The last argument _Options_ must be a list of options, which can be:
|
||||
+<b>filename</b>
|
||||
the filename for a module to import into the current module.
|
||||
|
||||
+ <b>library( +File )</b>
|
||||
a library file to import into the current module.
|
||||
|
||||
+ <b>hide( +Opt)</b>
|
||||
if _Opt_ is `false`, keep source code for current module, if `true`, disable.
|
||||
|
||||
+ <b>export(+PredicateIndicator )</b>
|
||||
Add predicates to the public list of the context module. This implies
|
||||
the predicate will be imported into another module if this module
|
||||
is imported with use_module/1 and use_module/2.
|
||||
|
||||
+ <b>export_list(? _Mod_,? _ListOfPredicateIndicator_)</b>
|
||||
The list _ListOfPredicateIndicator_ contains all predicates
|
||||
exported by module _Mod_
|
||||
|
||||
Note that predicates are normally exported using the directive
|
||||
`module/2`. The `export/1` argument is meant to allow export from
|
||||
dynamically created modules. The directive argument may also be a list
|
||||
of predicates.
|