This chapter describes the features of SWI-Prolog for delivering applications that can run without the development version of the system installed.
A SWI-Prolog runtime executable is a file consisting of two parts. The first part is the emulator, which is machine dependent. The second part is the resource archive, which contains the compiled program in a machine-independent format, startup options and possibly user-defined resources, see resource/3 and open_resource/3.
These two parts can be connected in various different ways. The most
common way for distributed runtime applications is to concatenate
the two parts. This can be achieved using external commands (Unix:
cat, Windows: copy), or using the
stand_alone option to qsave_program/2.
The second option is to attach a startup script in front of the resource
that starts the emulator with the proper options. This is the default
under Unix. Finally, an emulator can be told to use a specified resource
file using the -x commandline switch.
stand_alone option, the resource is headed
by the emulator, a Unix shell-script or nothing.
ListOfOptions is a list of <Key> = <Value> or <Key>(<Value>) pairs. The available keys are described in table 7.
| Key | Option | Type | Description |
| local | -L | K-bytes | Size (Limit) of local stack |
| global | -G | K-bytes | Size (Limit) of global stack |
| trail | -T | K-bytes | Size (Limit) of trail stack |
| argument | -A | K-bytes | Size (Limit) of argument stack |
| goal | -g | atom | Initialisation goal |
| toplevel | -t | atom | Prolog toplevel goal |
| init_file | -f | atom | Personal initialisation file |
| class | atom | If runtime,
only read resources from the state (default). If kernel,
lock all predicates as system predicates If development,
change the predicates in their current state and keep reading resources
from their source (if present). See also resource/3. | |
| autoload | bool | If true, run autoload/0 first | |
| map | file | File to write info on dump | |
| op | save/standard | Save operator declarations? | |
| stand_alone | bool | Include the emulator in the state | |
| emulator | file | Emulator attached to the (stand-alone) executable. Default is the running emulator. |
Before writing the data to file, qsave_program/2 will run autoload/0 to all required autoloading the system can discover. See autoload/0.
Provided the application does not require any of the Prolog libraries to be loaded at runtime, the only file from the SWI-Prolog development environment required is the emulator itself. The emulator may be built in two flavours. The default is the development emulator. The runtime emulator is similar, but lacks the tracer.
If the option stand_alone(on) is present, the emulator
is the first part of the state. If the emulator is started it will test
whether a boot-file (state) is attached to the emulator itself and load
this state. Provided the application has all libraries loaded, the
resulting executable is completely independent of the runtime
environment or location where it was build.
See also section 2.10.2.3.
qsave_program(File, []).
This predicate is used by qsave_program/[1,2] to ensure the saved state will not depend on one of the libraries. The predicate autoload/0 will find all direct references to predicates. It does not find predicates referenced via meta-predicates. The predicate log/2 is defined in the library(quintus) to provide a quintus compatible means to compute the natural logarithm of a number. The following program will behave correctly if its state is executed in an environment where the library(quintus) is not available:
logtable(From, To) :-
From > To, !.
logtable(From, To) :-
log(From, Value),
format('~d~t~8|~2f~n', [From, Value]),
F is From + 1,
logtable(F, To).
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However, the following implementation refers to log/2 through the meta-predicate maplist/3. Autoload will not be able to find the reference. This problem may be fixed either by loading the module libtary(quintus) explicitly or use require/1 to tell the system that the predicate log/2 is required by this module.
logtable(From, To) :-
findall(X, between(From, To, X), Xlist),
maplist(log, Xlist, SineList),
write_table(Xlist, SineList).
write_table([], []).
write_table([I|IT], [V|VT]) :-
format('~d~t~8|~2f~n', [I, V]),
write_table(IT, VT).
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