Inline::SLang - Write Perl subroutines in S-Lang.
use Inline SLang;
print "9 + 16 = ", add(9,16), "\n";
print "9 - 16 = ", subtract(9,16), "\n";
print JAxH('Inline'), "\n";
__END__
__SLang__
define add (a,b) { return a + b; }
define subtract (a,b) { return a - b; }
define JAxH () {
variable type = ();
return sprintf( "Just Another %S Hacker!", type );
}
The Inline::SLang module lets you write Perl subroutines in S-Lang. It dynamically translates the parameters and return values into native data types for both languages (or into Perl classes that are used to represent S-Lang types with no direct translation to Perl). This allows you to write a Perl script and take advantage of S-Lang whenever you wish: perhaps there is a S-Lang module that you wish to use, or you want to take advantage of a S-Lang function that you have written.
The module sets up an in-process S-Lang interpreter, runs your code, and then examines the interpreter's symbol table, looking for things to bind to Perl. The process of interrogating the S-Lang interpreter only occurs the first time you run your S-Lang code. The namespaces are cached, and subsequent calls use the cached version (which is hidden in the _Inline directory; see the Inline documentation for details of how the code is cached). Of course, your S-Lang code must still be run every time your run the Perl script -- but Inline::S-Lang already knows the results of running it.
From the S-Lang library home page at http://www.s-lang.org/
S-Lang is a multi-platform programmer's library designed to allow a developer to create robust multi-platform software. It provides facilities required by interactive applications such as display/screen management, keyboard input, keymaps, and so on. The most exciting feature of the library is the slang interpreter that may be easily embedded into a program to make it extensible.
For our purposes it is the S-Lang interpreter that we are interested in. See the Term::Slang module (on CPAN) if you want an interface to the terminal library provided by S-Lang.
Using Inline::SLang will seem very similar to using any other Inline language, thanks to Inline's consistent look and feel.
This section will explain the different ways to use Inline::SLang. Further details on configuring the behaviour of Inline::SLang can be found in Inline::SLang::Config. For more details on Inline, see Inline or perldoc Inline.
Using functions defined in S-Lang is just like using Perl subroutines. You just supply the source code to Inline::SLang - see the Inline manual for the various ways of doing this - and then use them in your Perl code. For example:
# set up a S-Lang function
use Inline SLang => <<'END';
define doit() { vmessage("Printing from S-Lang"); }
END
# now call the S-Lang function from Perl
doit;
By default all S-Lang functions - other than S-Lang intrinsic functions (the functions defined by the S-Lang interpreter, such as array_map() and assoc_get_keys()) - in the default namespace ("Global") are bound to Perl. The Perl functions are available in the main package.
The BIND_NS configuration option can be used to change the list of S-Lang namespaces bound to Perl. If you have need of an intrinsic S-Lang function then you can either write a wrapper routine or use the BIND_SLFUNCS option. See Inline::SLang::Config for more details.
Note that there are no checks that a S-Lang symbol, when mapped to Perl, does not clobber an existing value (or is a Perl built-in function so can not be over-ridden). So beware when you define a S-Lang function called open()!
If you have a S-Lang module that you want to use directly from Perl, it's as easy as the following (assuming the module is importable and called funkymodule):
use Inline 'SLang' => 'import("funkymodule");';
and then you can start using the functions defined by the module. You use a similar technique if you have a file containing S-Lang code that needs to be loaded via evalfile.
We currently do not bind any S-Lang variables to Perl. To access variables you have to write S-Lang routines that read/write the variable, as shown by the foo() and bar() routines below:
variable foobar = "a string";
define foo() { return foobar; }
define bar(x) { foobar = x; }
It should be possible to also bind variables, but this is not - and may never be - supported.
Inline::S-Lang attempts to seamlessly convert between Perl and S-Lang data types. For "simple" types - for example strings - where there is a direct match between S-Lang and Perl, the conversion is not noticeable. For more complicated types - such as complex numbers - S-Lang variables are converted to Perl objects. Where possible a perl-like interface is retained. See Inline::SLang::Types for more information on how the various data types are supported.
The module currently requires that yor S-Lang library has been compiled with support for both floating-point and complex numbers.
The module provides several utility functions which are discussed below. By default they are only available using fully-qualified names - e.g. Inline::SLang::sl_eval() - although the EXPORT configuration option can be used to change this.
$val = Inline::SLang::sl_array2perl(); $val = Inline::SLang::sl_array2perl( $newval );
Sets/Gets the current status of the "how do we convert a S-Lang array into Perl" flag. Returns the status.
We list the possible values of the flag below. For further details on array support in Inline::SLang see Inline::SLang::Array.
If PDL support was not compiled in to the module then the flag can either be 0 or 1, where
All arrays are converted to a Perl array reference.
All arrays are converted to a Perl Array_Type object
If PDL support is available then there are four options:
All arrays are converted to a Perl array reference.
All arrays are converted to a Perl Array_Type object
Numeric arrays are converted to piddles and non-numeric arrays are converted to a Perl array reference.
Numeric arrays are converted to piddles and non-numeric arrays are converted to a Perl Array_Type object.
$sl = Inline::SLang::sl_array( $aref ); $sl = Inline::SLang::sl_array( $aref, $adims ); $sl = Inline::SLang::sl_array( $aref, $atype ); $sl = Inline::SLang::sl_array( $aref, $adims, $atype );
This is a wrapper around the Array_Type constructor and is intended to make it easy to ensure that a Perl array reference is converted into a S-Lang array of the correct type, dimensionality, and size.
The data is stored in $aref, a Perl array reference. If no other parameters are supplied then the array dimensions, size, and type are guessed from $aref. Since Perl has such a flexible type system the routine can sometimes make a surprising choice for the data type of the array, so it may well be worth supplying the array type as $atype - which can be either a string containing the name of the S-Lang datatype, such as "Int_Type", or a DataType_Type object.
If you know the array dimensions then it's probably faster to supply them as the $adims argument, which should be an array reference.
Note that there is limited error checking in this routine: if $aref is a 2x3 array but you send in $adims as [3,2] - or [24] say - then expect weird behaviour (at the very least).
use Inline 'SLang' => Config => EXPORT => [ "sl_array" ]; use Inline 'SLang'; ... some_slang_func( sl_array([[1.0,0.0],[0.0,1.0]],"Double_Type") );
For numeric types I expect most people to use piddles. This routine is more useful for arrays of non-numeric data types.
[ retval(s) = ] Inline::SLang::sl_eval( $str );
This function evaluates the supplied S-Lang code (in $str) and converts any return values to Perl. In general this will not be needed, since you can always call S-Lang's eval() function via a wrapper function (or by binding it to a different function name in Perl). One approach is shown in the last example below.
One time it can come in useful is to access a S-Lang variable (either to set its value or store its value in a Perl variable).
# get the version of the S-Lang library
my $sl_ver = Inline::SLang::sl_eval( "_slang_version" );
# set a variable in S-Lang scope (assuming 'this_var exists')
Inline::SLang::sl_eval( "this_var = 23.5" );
# evaluate arbitraty S-Lang code
my $foo = Inline::SLang::sl_eval("23+4");
print "S-Lang thinks 23+4 is $foo\n";
A more flexible solution is to write a S-lang wrapper around the S-Lang eval() function (perhaps this functionality should be moved into sl_eval?):
% Call as myeval( "slang code" [, var1, var2, ... ] );
% where varX are variables that placed onto the S-Lang
% stack before calling the S-Lang code
define myeval() {
% pop off the slang code from the stack, leave the rest there
variable slcode;
if ( _NARGS > 1 ) {
_stk_reverse(_NARGS);
slcode = ();
_stk_reverse(_NARGS-1);
}
else
slcode = ();
eval( slcode );
}
$flag = Inline::SLang::sl_have_pdl();
Returns 1 if the module was compiled with support for PDL, and 0 otherwise.
$type = Inline::SLang::sl_typeof( $var );
Returns the S-Lang type of the data stored in the Perl variable $var. This should be more efficient than using S-Lang's typeof() command since it does not require the conversion of the whole variable to S-Lang (normally not a big issue but it can be if $var contains a large array or a complicated structure).
The return value is an object of the DataType_Type class; see PDL::Types for more information on how S-Lang variables are represented in Perl.
my $foo = some_slang_function(); my $type = Inline::SLang::sl_typeof($foo); print "The function returned a $type variable\n";
Note that all objects used to represent S-Lang data types - other than Math::Complex objects - have a typeof() method which can be used to find the type of the object.
$ver = Inline::SLang::sl_version();
Returns, as a string, the version of S-Lang against which the module was compiled, with a format of "a.b.c". You can use sl_eval("_slang_version_string") to find out what version of the library you are using.
The module will refuse to build if there is an error in the S-Lang code compiled when your program is first run. If an error occurs in the S-Lang interpreter - such as calling a function that expects an argument with none - then the S-Lang error is transformed into a Perl error (as a call to croak) and the S-Lang interpreter is restarted. This means that these errors can be handled by using Perl's eval statement.
This is intended to be the last release before the release of version 1.00.
I have decided to stick with the differences between the indexing of multi-dimensional arrays in PDL and S-Lang: a 2x3 element piddle will be converted to a 3x2 element S-Lang array.
The PDL support has been upgraded to better-handle virtual piddles, such as slices of another piddle. The current approach has the side effect of calling PDL's make_physical() method on the piddle, which results in extra memory use.
Minor bug fixes to Makefile.PL.
Minor documentation fixes - including exampes/array_conversion.pl - and improvements to Inline::SLang::Details - including the addition of examples/order.pl.
Fixed a bug which caused t/11type_synonyms.t to fail on some machines.
The S-Lang interpreter is now initialised with the min, max, sum and cumsum functions as part of the S-Lang run-time library (cumsum is only available if you have v1.4.9 of S-Lang).
Another one-line fix and PDL support works on OS-X. PDL support is now the default option (if available) when building Inline::SLang.
A one-line fix means that PDL support now works on Linux as well as Solaris. It works on OS-X until you try to convert a S-Lang array to a piddle. PDL support is now on by default for Solaris and Linux machines.
This is a bug-fix for make test in version 0.22, which failed on systems which did not already have Inline::SLang installed.
The build process has been changed to use Inline::C to embed C code within Makefile.PL, rather than having it in a separate file which we have to compile ourselves. This should hopefully make the build process a bit more portable.
This release will now build on OS-X machines. The support for PDL has been turned off by default - even if PDL is installed on your system - since it does not work on Linux and OS-X machines.
The main changes are behind the scenes, and involve splitting the code up and making a tad more modular.
This release begins support for the Perl Data Language in Inline::SLang. Please note that it is a work-in-progress.
This is a minor upgrade in functionality to version 0.11; the changes are made to help support the inclusion of PDL in a future release. The changes are:
DataType_Type class for numeric types that are - or may be - synonyms of the "base" types. The added types are: Int16_Type, Int32_Type, their unsigned versions, Float32_Type, Float64_Type, and - if they are not a "base" type - Short_Type and Long_Type.This release makes a couple of improvements to version 0.10 and includes infrastructure changes to support PDL (although piddles are still not supported). The major changes are:
Array_Type object as well as array references. The behaviour is controlled by the Inline::SLang::sl_array2perl() function, described in Inline::SLang.DataType_Type object: use the functions Inline::SLang::<datatype name>() instead of DataType_Type->new( "<datatype name>" );. Use '!types' in the EXPORT configuration option to import all these functions.DataType_Type objects can now be compared for equality (==, eq) and inequality (!=, ne).There have been a number of significant enhancements and changes in this release, which is why the release number has been bumped-up to the lofty heights of 0.10.
The really-short summary is that all variables should now be supported and the support for S-Lang's associative arrays, normal arrays, and structures has been made much -more Perl like.
Inline::SLang::XXX to XXX.Struct_Type and named structs) are stored using a Perl object (also called Struct_Type) which can be treated as a hash reference. As an example, if the S-Lang structure has a field x and it is stored in the Perl variable $foo then you can access the field as $$foo{x}.Assoc_Type arrays are now converted to the Perl Assoc_Type class (and vice-versa). This object can be treated as a hash reference. When calling S-Lang functions, hash references are converted to S-Lang as an Assoc_Type [Any_Type] array.Array_Type objects) and S-Lang (Array_Type variables) for any S-Lang data type. Any dimension of array supported by S-Lang is now available (in previous only one and two dimensional arrays could be used).
Support for piddles is not yet available (planned soon).
croak). This means that calling DataType_Type->new() with an unknown type name no longer results in S-Lang error messages printed to STDERR (which it did in 0.06).Notable changes are:
Inline::SLang::XXX where XXX equals the name of their S-Lang data type. Essentially all you can do with these objects is pass them back to S-Lang routines. However, it does mean you can now call routines that return module-defined types.
Currently the S-Lang file types (so File_Type and FD_Type) are converted using this scheme, which means you can not use them with Perl I/O commands. I need to read up a lot more on Perl's I/O mechanism before I can change this (if it's possible).
Foo_Type created by typedef struct {...} Foo_Type; - are now handled as Inline::SLang::XXX objects, where XXX matches the structure type (so Foo_Type in this example). These classes are sub-classes of Inline::SLang::Struct_Type.Notable changes are:
DataType_Type variables - has been changed to use a scheme in which the Perl class name is formed from the concatanation of Inline::SLang:: and the S-Lang type (so Inline::SLang::struct has been renamed to Inline::SLang::Struct_Type).
The classes are also more uniform in that they have a number of common functions and, where possible, the method names are similar to S-Lang functions with the same functionality.
Inline::SLang::Ref_Type class. Unfortunately this requires use of function/types that are not part of the public interface of the S-Lang library.Notable changes are:
BIND_NS configuration option to allow functions in other namespaces to be bound as well. Use the Inline '-MInline=INFO' option to find out what functions have been bound.Struct_Type variables are converted to Inline::SLang::struct objects. There are memory leaks!Assoc_Type arrays to Perl.Struct_Type variables are converted to Inline::SLang::struct objects.Initial public release
Please use the CPAN Resource Tracker at http://rt.cpan.org/NoAuth/Bugs.html?Dist=Inline-SLang to check for bugs, report new ones, and request new features.
Inline::SLang::Config, Inline::SLang::Types, Term::Slang
For information about using Inline, see Inline.
For information about other Inline languages, see Inline-Support.
For information about S-Lang see http://www.s-lang.org/.
John Davis (for S-Lang), Brian Ingerson (for the Inline framework), and Neil Watkiss since I based much of this module on his Inline::Python and Inline::Ruby modules.
However, please do not assume that any errors in this module are in any way related to the above people.
Doug Burke <djburke@cpan.org>
This software is Copyright (C) 2003, 2004 Smithsonian Astrophysical Observatory. All rights are reserved.
It is released under the GNU General Public License. You may find a copy of this licence in the file LICENSE within the source distribution or at http://www.fsf.org/copyleft/gpl.html
Prior to version 0.04 the module was distributed under the same terms as Perl.
There is no warranty. Please see the GNU General Public License for more details.
