[ ECLiPSe Prolog Environment built-in.|Group Index| Full Index]

get_flag(?Flag, ?Value)

Succeeds if the flag Flag has the value Value.

?Flag
Atom or Variable.
?Value
Prolog term.

Description

Used to return or check the environment flag Flag with value Value. The environment flags which are read/write may be updated using set_flag/2. The current values of the environment flags are returned by env/0.

The following list details the environment flags:

all_dynamic

Access mode : read/write

Type : Atomic constant on or off

Default : off

Description : Specifies whether all clauses compiled are dynamic or not. Mainly for test purposes.

break_level

Access mode : read/write

Type : Integer

Description : Specifies current nesting level of recursive top-level loops.

coroutine

Access mode : read/write

Type : Atomic constant on or off

Default : configuration dependent

Description : Specifies whether built-in predicates delay or raise instantiation faults.

cwd

Access mode : read/write

Type : String

Description : Specifies the name of the current working directory. May also be set using cd/1 or read using getcwd/1.

debug_compile

Access mode : read/write

Type : Atomic constant on or off

Default : on

Description : Specifies whether clauses are compiled for debugging or not. May be set on by dbgcomp/0 or off by nodbgcomp/0.

debugging

Access mode : read-only

Type : Atomic constant nodebug, creep, or leap

Default : nodebug

Description : Specifies whether debugging is disabled (nodebug) or enabled. trace/0 sets the creep mode, debug/0 sets the leap mode.

debugger_model

Access mode : read-only

Type : Atomic constant

Default : eclipse

Description : This flag is obsolete. There used to be different debugger models. Now it is always 'eclipse'.

dfid_compile

Access mode : read/write

Type : Atomic constant on or off

Default : off

Description : When on, the compiler will generate code that keeps track of the number of ancestors of each goal. This is used by library(dfid) to perform bounded depth-first search and iterative deepening.

enable_interrupts

Access mode : read/write

Type : Atomic constant on or off

Default : on

Description : If on, interrupts are recognised and processed as they occur. If off, interrupts are entered into a delay queue and processed only when the flag is switched back to on. Interrupts should be disabled only for short periods of time in order to keep the system's interrupt response time short.

extension

Access mode : read-only

Type : Atomic constant.

Default : configuration dependent

Description : Specifies which extensions are available in the system. This flag may contain multiple values and will return them on backtracking.

float_precision

Access mode : read/write

Type : Atomic constant single or double

Default : double

Description : Specifies whether the system uses single or double precision floating point numbers. Should be set at the beginning of a session.

gc

Access mode : read/write

Type : Atomic constant on, verbose or off

Default : on

Description : Specifies whether garbage collection is enabled (on), disabled (off) or enabled and reports every collection on toplevel_output (verbose).

gc_interval

Access mode : read/write

Type : Integer

Default : 1/8 of global stack size, at least 1MB

Description : Specify how often the collector is invoked. Roughly, the argument specifies how many bytes a program can use up before a garbage collection is triggered. If the garbage collector runs frequently while reclaiming little space it may make sense to increase gc_interval, thus reducing the number of garbage collections.

gc_interval_dict

Access mode : read/write

Type : Integer

Default : 960

Description : Specify after how many new dictionary entries the dictionary garbage collector is invoked.

goal_expansion

Access mode : read/write

Type : Atomic constant on or off

Default : on

Description : Specifies whether goal expansion is done by the compiler. This includes compiler inlining and goal macro transformations. Can be disabled for debugging purposes.

hostarch

Access mode : read-only

Type : String

Description : String identifying the host processor and operating system. It is also the name of the machine-dependent subdirectories in the ECLiPSe installation.

hostid

Access mode : read-only

Type : String

Description : The unique identification of the host machine that the system is running on.

hostname

Access mode : read-only

Type : string

Description : The name of the current host machine.

ignore_eof

Access mode : read/write

Type : Atomic constant on or off

Description : Controls whether ECLiPSe can be exited by typing an end-of-file to the toplevel-prompt or whether this is ignored. If ignored, ECLiPSe can be exited by calling halt/0.

installation_directory

Access mode : read-only

Type : string

Description : The name of the toplevel directory of the running ECLiPSe installation. All ECLiPSe library, documentation and other directories are below this one.

last_errno

Access mode : read-only

Type : Integer

Description : The error code that the most recent failed operating system call returned. This should no longer be used because of portability problems, use errno_id/1 instead.

library_path

Access mode : read/write

Type : List of strings

Default : the contents of the user's ECLIPSELIBRARYPATH environment variable, followed by the system library directories

Description : Specifies the list of pathnames used by the system to search for library files. The library path is used by lib/1,2, for autoloading, and to expand library/1 structures in pathnames.

loaded_library

Access mode : read/write

Type : Atom

Description : Returns the names of the currently loaded libraries. This flag may contain multiple values and will return them on backtracking.

macro_expansion

Access mode : read/write

Type : Atomic constant on or off

Default : on

Description : Specifies whether macro expansion used by the source transformation facility is enabled or disabled. Should be disabled only for debugging purposes.

max_global_trail

Access mode : read-only

Type : Integer

Description : The maximum size in bytes to which the global/trail stack can grow. See also statistics/2.

max_local_control

Access mode : read-only

Type : Integer

Description : The maximum size in bytes to which the global/trail stack can grow. See also statistics/2.

max_predicate_arity

Access mode : read-only

Type : Integer

Default : 255

Description : Returns the maximum number of arguments allowed for an ECLiPSe predicate.

object_suffix

Access mode : read-only

Type : String

Description : Returns the suffix of the external object files that can be loaded using load/1. It is usually "so" for systems that support shared libraries and "o" for the others.

occur_check

Access mode : read/write

Type : Atomic constant on or off

Default : off

Description : If the flag is on, occur check is performed on uncompiled unifications and the compiler generates code for unifications that will perform the occur check when necessary.

output_mode

Access mode : read/write

Type : String

Default : "QPm"

Description : The value is a control string that is recognised by the %w format of printf/3. This format is used to output results on the toplevel loop and to print debugger trace lines.

pid

Access mode : read-only

Type : Integer

Description : Returns the process identifier of the current ECLiPSe .

ppid

Access mode : read-only

Type : Integer

Description : Returns the process identifier of the current ECLiPSe 's parent process.

prefer_rationals

Access mode : read/write

Type : Atomic constant on or off

Default : off

Description : Specifies if the result of a /-division of two integers gives a rational or a floating point result. Similar for the result of raising an integer to a negative integral power.

print_depth

Access mode : read/write

Type : Integer

Default : 20

Description : Specifies the print depth bound for printing compound terms. It can also be set by the '<' option of the debugger. It is not taken into account by writeq/1, 2, other I/O built-ins obey this flag.

prolog_suffix

Access mode : read/write

Type : List of strings

Default : ["", ".sd", ".ecl", ".pl"]

Description : Specifies the Prolog source file suffix(es) used when compiling files or loading libraries. The system tries to find the file by appending the given suffixes in the order provided.

syntax_option

Access mode : read/write

Type : Atom

Description : Returns the names of the currently enabled syntax options. This flag may contain multiple values and will return them on backtracking. A syntax option is reset using set_flag(syntax_option, not(Flag)). Most compatibility packages affect these flags as well. The following options are available:

*based_bignums - Allow base notation even for integers longer than the wordsize (i.e. they are always positive).

*blanks_in_nil - allow blanks between the brackets in [].

*dense_output - try to reduce blankspaces printed around operators.

*limit_arg_precedence - do not allow terms with a precedence higher than 999 as structure arguments, unless parenthesised.

*nested_comments - allow bracketed comments to be nested.

*nl_in_quotes - allow newlines to occur inside quotes.

*no_array_subscripts - do not allow array subscript syntax for subscript/2

*no_blanks - do not allow blanks between functor an opening parenthesis

*no_other_quotes - do not allow string quotes inside atom quotes and vice versa.

*$VAR - terms of the form '$VAR'(N) are printed in a special way by all the predicates that obey operator declarations (i.e. write, writeq, print and partly printf). '$VAR'(0) is printed as A, '$VAR'(25) as Z, '$VAR'(26) as A1 and so on. When the argument is an atom or a string, just this argument is printed.

toplevel_module

Access mode : read/write

Type : Atom

Default : eclipse

Description : The name of the current top-level module. This is the caller module for all queries entered in the top-level loop. By default, this is also shown in the top-level prompt.

unix_time

Access mode : read-only

Type : Integer

Description : Return the time as given by the UNIX time(3) function, ie. seconds since 00:00:00 GMT, Jan 1 1970.

variable_names

Access mode : read/write

Type : Atomic constant on, off or check_singletons

Default : check_singletons

Description : Controls the ability to retain the source name of variables. This flag affects the reading process only, i.e. when a variable is read (or compiled) with the flag set to on, it will keep its name even when the flag is switched off later. check_singletons is like on but additionally the compiler emits warnings about source variables which occur only once in a clause and whose name does not start with an underscore. The source variable names are being created during the term input if this flag is not off, and then they are kept independently of the value of this flag.

version

Access mode : read-only

Type : Atom

Description : Returns the current version number of ECLiPSe .

worker

Access mode : read-only

Type : Integer

Description : In a parallel session it returns a positive number, identifying the worker on which the flag inquiry was executed. In a sequential session 0 is returned.

workers

Access mode : read/write

Type : A structure Host:N, where Host is an atom and N integer

Description : In a parallel session it returns a positive number for N, which is the number of active workers on a given host Host. If Host is a variable, it is bound to the host name where this predicate is executed.

workerids

Access mode : read-only

Type : A structure Host:ActiveList+AsleepList, where Host is an atom and ActiveList and AsleepList are integer lists

Description : In a parallel session it returns the workerid lists of of both active and asleep workers on a given host Host. If Host is a variable, it is bound to the host name where this predicate is executed.

wm_window

Access mode : read/write

Type : Atomic constant on and off

Description : In a parallel session this flag tells if the window interface for the worker manager is on or off.

Fail Conditions

None.

Resatisfiable

Yes.

Exceptions

(5) Type error
Flag is neither an atom nor variable.

Examples


Success:
   [eclipse]: get_flag(float_precision, X).
   X = double

   yes.
   [eclipse]: get_flag(loaded_library, L).

   L = lists     More? (;)

   L = development_support     More? (;)
   yes.

Error:
   get_flag(1,X).           (Error 5)


See Also

set_flag / 2, env / 0, errno_id / 1