MATLAB POLYSPACE RELEASE NOTES Manuale Utente Scaricare il pdf (Pagina 164)

4 Programming

Like other functions, a neste d function has its own workspace where variables

used by the function are stored. B ut it also has a ccess to the w orkspaces

of all functions in which it is nested. So, for example, a variable that has

a value assigned to it by the primary function can be read or overwritten

by a function nested at any level w ithin the prim ary. Similarly, a variable

that is assigned in a nested function can be read or overwritten by any of the

functions containing that function.

Function Overloading

Overloaded functions act the same way as overloa d ed fun cti on s in most

computer languages. Overloaded functions are useful when you need to create

a function that responds to different types of inputs accordingly. For instance,

you might want one of your functions to accept both double-precision and

integer input, but to handle each type somewhat differently. You can make

thisdifferenceinvisibletotheuserbycreating two separate functions having

thesamename,anddesignatingonetohandle

double types and one to

handle integers. When you call the function, MATLAB chooses which M-file

to dispatch to based on the type of the input arguments.

Global Variables

If you want more than one function to share a single copy of a variable, simply

declare the variable as

global in all the functions. Do the same thing at

the command line if you want the base w orkspace to access the variable.

The global declaration must occur before the variable is actually used in a

function. Although it is not required, using capital letters for the names of

global variables helps distinguish them from other variables. For example,

create an M-file called

falling.m:

function h = f alling(t)

global GRAVITY

h = 1/2*GRAVITY*t.^2;

Then interactively enter the statements

global GRAVITY

GRAVITY = 32;

y = falling((0:.1:5)') ;

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MATLAB POLYSPACE RELEASE NOTES Manuale Utente Pagina 164