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WMLScript Functions: Declaration, Libraries, and Recursion, Slides of Fundamentals of E-Commerce

Fakir Mohan UniversityFundamentals of E-Commerce

An introduction to wmlscript functions, including how to declare them, use libraries, and implement recursion. It covers topics such as variable types, initialization, conditions, and common language statements.

Typology: Slides

2012/2013

Uploaded on 07/29/2013

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WMLScript - Functions
Within each function, you’ll write WMLScript
code.
Syntax:
var n = 1; // Declares a variable named ‘n’
n = 2; // Assigns n the value 2
if (n==3) ... // Test if n equals 3.
// Note that ‘=‘, assignment, is not the
// same as ‘==‘, which tests equality.
You’ve got the full set of if-then tests, loops and so on...
for (var index = 0; index < 100; index++) {
myFunc(index);
};
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Download WMLScript Functions: Declaration, Libraries, and Recursion and more Slides Fundamentals of E-Commerce in PDF only on Docsity!

WMLScript - Functions

Within each function, you’ll write WMLScriptcode.

Syntax:

var n = 1;

// Declares a variable named ‘n’

n

// Assigns n the value 2

if (n==3) ...

// Test if n equals 3.// Note that ‘=‘, assignment, is not the// same as ‘==‘, which tests equality.

You’ve got the full set of

if-then

tests, loops and so on...

for

(var

index

index

index++)

myFunc(index);

WMLScript - Functions

Declaring a function of your own:

Ex:

extern function getHello(){

return “hello!”;

Ex:

extern function addOne(n){

return n+1;

Ex:

extern function addVals(n, m){

return n+m;

WMLScript - Functions

The WMLScript Libraries:

Lang (miscellaneous routines)

Float (real numbers)

String (character string manipulation)

URL (HTTP string routines)

WMLBrowser (browser interraction)

Dialogs (user interraction)

Console (debug output)

Each library defines a set of functions that can becalled from your code.

For details on each library, consult the referencematerials online.

WMLScript - Functions

A few common standard library routines:

^

WMLBrowser.getVar()

// gets a var’s value

^

WMLBrowser.setVar(, )

// sets a var’s value

^

WMLBrowser.refresh()

// reload this page

^

WMLBrowser.go(url)

// go to a url

^

Lang.isInt()

// Test for a number

^

Lang.parseInt()

// Convert to a number

Some common language statements:

^

if () else

^

for (; ; ) ...

^

while () ...

^

return ;

// Sets the value of// a function call

WMLScript - Calling WMLS from WML

extern function increment() {

var myVar = WMLBrowser.getVar("myVar");WMLBrowser.setVar("myVar",

myVar + 1

WMLBrowser.refresh();

What’s going

on here?

WMLScript - What happened back there?

Variable types

The problem was that variables in WMLScript don’t have a type

associated with them. WMLS doesn’t know whether

they’re character strings or numbers.

Since “+” will add two numbers

or

glue together two strings

(1+1=2, but ‘abc’+’def’=‘abcdef’), WMLS just assumed wewanted string concatenation.

To make sure we use integer math, use the

Lang

library’s

toInt()

function to force the variable type to an integer:

extern function increment() {

var myVar = WMLBrowser.getVar("myVar"); if (!Lang.isInt(myVar))

myVar = 0;

WMLBrowser.setVar("myVar",

Lang.parseInt(myVar) + 1

WMLBrowser.refresh();

WMLScript - Initialisation and conditions

Testing a value in WMLS:

extern

function

testValue() {

var

myVar =

Lang.parseInt(WMLBrowser.getVar("myVar"));

if

(((myVar

/^

myVar)

WMLBrowser.setVar("myOddity", "even"); else

WMLBrowser.setVar("myOddity", "odd"); WMLBrowser.refresh();

And the result:

WMLScript - Recursion

“Recursion”

Recursion is the term for when a function calls itself. Whenyou write recursive code, take care : make sure that there’salways a way out!

Ex:

In mathematics, the phrase “N factorial” means “if N is some

number, then multiply all of the numbers from 1 to Ntogether”. You could say that a little more easily as “if Nis some number, then multiply N times N minus one,factorial”. You’ve defined factorial in terms of itself.

The shorthand for factorial is !. “N!” is “N factorial”.In other words, N!= N * (N-1)!.

WMLScript - Recursion

<card

id="card1"> <onevent

type="onenterforward">

<setvar

name="nFact"

value="<untested>"

Enter N

:^

<input

name="n"

format="N*N"/>

Click here

to

find N!

("N

factorial").


N!

$(nFact).

extern

function

factorial()

var

n^

Lang.parseInt(WMLBrowser.getVar("n")); if

(n

n^

=^

WMLBrowser.setVar("nFact",

recurseFactorial(n)

WMLBrowser.refresh(); } extern

function

recurseFactorial(n)

if

(n

return

n

recurseFactorial(n-

else

return

n;