Module for overloading Scilab functions

• What is it?
• How does it work?
• Installation

What is it ?

Overloading means that, when a function is invoked with an object as input argument, it is not the standard funtion which is applied but a version specific to the considered object.

For example, a function func specific to a typ-object must be named %typ_func (prefix %typ_). If x is a typ-object, typing func(x) will invoke automatically %typ_func(x).

What is called "object" here consists of a Scilab mlist (see help mlist). For example, a sym-object looks like x = mlist(['sym','str1'],'xxxxxx'), x.str1 is equal to 'xxxxxx'.

A large number of Scilab built-in functions (not all unfortunately) take overloading into account. Examples of such functions: size, real, imag, abs, conj, log, exp, sqrt, cos, sin, acos, asin....

This module permits the user to overload most non-built-in functions. It is a complement to the Symbolic Toolbox and to the Linear Fractional Representation Toolbox but it can also be used for any kinds of user-defined objects.

How does it work?

Two main files:

• updater.sce: Scilab script which generates automatically all the files required for overloading. This script can be customized by defining a modified list of the functions which must become overloadable. The default list is consistent with the Symbolic Toolbox and the Linear Fractional Representation Toolbox.
• overloader.sci: Scilab function. This function checks the nature of the first input argument of invoked functions (if in the list defined in the above script) and invokes the relevant function (note that currently only the first input argument is considered for this test).

The functions listed in updater.sce are treated as follows (three cases):

• Built-in functions are ignored.
• Existing Scilab function case: The original function is copied in OVLD/macros and renamed with the prefix %old_, in addition, this prefix is also added to the function name inside the file. A new file having the original name is created in OVLD/macros but this new function just calls overloader.sci which selects the function to be really invoked (add prefix %old_ or a prefix corresponding to the object class of the first input argument).
• Non-existing Scilab function case: As above, except that the file with prefix %old_ only contains an error message.

Installation.

• If this module is used only as a complement of the Symbolic Toolbox or of the Linear Fractional Representation Toolbox, skip this item. Otherwise, open the file updater.sce in a text editor and modify the vector of strings containing the names of the functions to be overloaded. Finally From the 'file' menu of a Scilab window, navigate to the directory OVLD where this module was unzipped and execute updater.sce.
• From the 'file' menu of a Scilab window, navigate to the directory OVLD where this module was unzipped and execute builder.sce and then, loader.sce.