Free based software for linux

Math::Symbolic::Base is a case class for symbols in symbolic calculations.

SYNOPSIS

use Math::Symbolic::Base;

This is a base class for all Math::Symbolic::* terms such as Math::Symbolic::Operator, Math::Symbolic::Variable and Math::Symbolic::Constant objects.

METHODS

Method to_string

Default method for stringification just returns the objects value.

Method value

value() evaluates the Math::Symbolic tree to its numeric representation.

value() without arguments requires that every variable in the tree contains a defined value attribute. Please note that this refers to every variable object, not just every named variable.

value() with one argument sets the objects value (in case of a variable or constant).

value() with named arguments (key/value pairs) associates variables in the tree with the value-arguments if the corresponging key matches the variable name. (Can one say this any more complicated?) Since version 0.132, an alternative syntax is to pass a single hash reference.

Example: $tree->value(x => 1, y => 2, z => 3, t => 0) assigns the value 1 to any occurrances of variables of the name "x", aso.

If a variable in the tree has no value set (and no argument of value sets it temporarily), the call to value() returns undef.

Method signature

signature() returns a trees signature.

In the context of Math::Symbolic, signatures are the list of variables any given tree depends on. That means the tree "v*t+x" depends on the variables v, t, and x. Thus, applying signature() on the tree that would be parsed from above example yields the sorted list (t, v, x).

Constants do not depend on any variables and therefore return the empty list. Obviously, operators dependencies vary.

Math::Symbolic::Variable objects, however, may have a slightly more involved signature. By convention, Math::Symbolic variables depend on themselves. That means their signature contains their own name. But they can also depend on various other variables because variables themselves can be viewed as placeholders for more compicated terms. For example in mechanics, the acceleration of a particle depends on its mass and the sum of all forces acting on it. So the variable acceleration would have the signature (acceleration, force1, force2,..., mass, time).

If youre just looking for a list of the names of all variables in the tree, you should use the explicit_signature() method instead.

Method explicit_signature

explicit_signature() returns a lexicographically sorted list of variable names in the tree.

See also: signature().

Method set_signature

set_signature expects any number of variable identifiers as arguments. It sets a variables signature to this list of identifiers.

Method implement

implement() works in-place!

Takes key/value pairs as arguments. The keys are to be variable names and the values must be valid Math::Symbolic trees. All occurrances of the variables will be replaced with their implementation.

Method replace

First argument must be a valid Math::Symbolic tree.

replace() modifies the object it is called on in-place in that it replaces it with its first argument. Doing that, it retains the original object reference. This destroys the object it is called on.

However, this also means that you can create recursive trees of objects if the new tree is to contain the old tree. So make sure you clone the old tree using the new() method before using it in the replacement tree or you will end up with a program that eats your memory fast.

fill_in_vars

This method returns a modified copy of the tree it was called on.

It walks the tree and replaces all variables whose value attribute is defined (either done at the time of object creation or using set_value()) with the corresponding constant objects. Variables whose value is not defined are unaffected. Take, for example, the following code:

$tree = parse_from_string(a*b+a*c);
$tree->set_value(a => 4, c => 10); # value of b still not defined.
print $tree->fill_in_vars();
# prints "(4 * b) + (4 * 10)"

Method simplify

Minimum method for term simpilification just clones.

Method descending_operands

When called on an operator, descending_operands tries hard to determine which operands to descend into. (Which usually means all operands.) A list of these is returned.

When called on a constant or a variable, it returns the empty list.

Of course, some routines may have to descend into different branches of the Math::Symbolic tree, but this routine returns the default operands.

The first argument to this method may control its behaviour. If it is any of the following key-words, behaviour is modified accordingly:

default -- obvious. Use default heuristics.

These are all supersets of default:
all -- returns ALL operands. Use with caution.
all_vars -- returns all operands that may contain vars.

Webmin is a web-based interface for system administration for Unix.

Using any browser that supports tables and forms, you can setup user accounts, internet services, DNS, file sharing and so on.

Rule Set Based Access Control (RSBAC) is a Free Software security extension for current Linux kernels. Rule Set Based Access Control is based on the Generalized Framework for Access Control (GFAC) by Abrams and LaPadula and provides a flexible system of access control based on several modules.
All security relevant system calls are extended by security enforcement code. This code calls the central decision component, which in turn calls all active decision modules and generates a combined decision. This decision is then enforced by the system call extensions.
Main features:
- Free Open Source (GPL) Linux kernel security solution
- Independent of governments and big companies
- Several well-known and new security models, like MAC, ACL and RC
- On-access virus scanning with the Dazuko interface
- Detailed control over individual user and program network accesses
- Fully access controlled kernel level user management
- Any combination of security models possible
- Easily extensible: write your own model for runtime registration
- Support for latest kernels and stable for production use
Enhancements:
- This release relates to kernel 2.4.34.5 and 2.6.22.1.
- There are important fixes with some compilation errors and an important bug with User Management password hashing, introduced with the newer 2.6 kernel crypto API.
- Some security has been added with safety measures against null pointers.

Sussen is a tool that checks for vulnerabilities and configuration issues on computer systems. It is based on the Open Vulnerability and Assessment Language.

base::ball - "b" all the namespaces under the given one(s).

SYNOPSIS

use base::ball qw(Foo::Utils);

equivalent to:

use base qw(Foo::Utils);
use base qw(Foo::Utils::Data);
use base qw(Foo::Utils::UI);
use base qw(Foo::Utils::Sys);
use base qw(Foo::Utils::Sys::Unix);
use base qw(Foo::Utils::Sys::Win32);
use base qw(Foo::Utils::Run);

Recursively searches the directory that the given name spaces are in to also use base on their "child" name spaces based on any .pm files found and any directories that belong to that .pm

In other words, assuming that the Foo/ that Foo::Utils is in has:

Utils/Data.pm, Utils/UI.pm, Utils/Sys.pm, Utils/Sys/Unix.pm, Utils/Sys/Win32.pm, Utils/Run.pm

then the synopsis is correct.

Note it does not follow directories who do not firts have a .pm, in other words:
Foo/Utils/Whatever/Fiddle.pm will no get Foo:Utils::Whatever::Fiddle as base unless Foo/Utils/Whatever.pm exists (and therefore Foo::Utils::Whatever is a base)

This is by design for good reasons and given enough popular demand may lead to support for it.

EiffelVision 2 is a platform independent GUI library.

EiffelVision2 is a nice GUI toolkit abstraction that works on multiple platforms. Based on GTK for Unix and WEL on Windows.