1. 1. WML and Wap-2 1. What are the problems in WML? WML which is infested with myriad problems. They are as follows: (a) it is static in nature. (b) Even though it has the concept of variables, initializing these variables is not as simple as it is in any other programming languages. (c) It doesn't support the features that other programming languages do. As a consequence, you cannot write a code that is dynamic. Dynamic in this context means, the ability to modify the behavior of the program while it is running. Therefore, WML is similar to HTML. In both cases, you cannot write programs, which have sufficient inbuilt intelligence.WML also fails to offer you the requisite level of flexibility. 2.What are the features of WML script Language? Some basic syntactical features of the language are: The smallest unit of execution in WMLScript is a statement and each statement must end with a semicolon (;). The following code is taken from the earlier "Hello World" example. You can see that the two WMLScript statements in this function have been ended with semicolons. extern function helloWorld() { WMLBrowser.setVar("message", "Hello World. Welcome to our WMLScript
2. 2. tutorial."); WMLBrowser.refresh(); } WMLScript is case-sensitive. a WMLScript function with the name WMLScript_Function is different from wmlscript_function. So, be careful of the capitalization when defining or referring to a function or a variable in WMLScript. Comments can either be single-line (beginning with //) or multi-line (bracketed by /* and */). This syntax is identical to both C++ and Java. There are two types of comments in WMLScript: single-line comment and multi-line comment. To add a single-line comment, begin a line of text with the // characters. To add a multi-line comment, enclose the text within /* and */. These rules are the same in WMLScript, JavaScript, Java, and C++. The WMLScript engine will ignore all comments. The following WMLScript example demonstrates the use of comments: extern function helloWorld() { // This is a single-line comment. /* This is a multi-line comment. */ /* A multi-line comment can be placed on a single line. */ WMLBrowser.setVar ("message", "Hello World. Welcome to our WMLScript tutorial."); WMLBrowser.refresh (); // A comment can be placed at a statement's end.
3. 3. } A literal character string is defined as any sequence of zero or more characters enclosed within double ("") or single () quotes. Boolean literal values correspond to true and false. New variables are declared using the var keyword (i.e. var x ;) 3. What is an operator? What are the operators supported by WML Script? Explain with examples. An operator is essentially a predefined function that is a part of the WMLScript language. WMLScript supports a variety of operators that support value assignment operations, arithmetic operations, logical operations, string operations, comparison operations, and array operations WML Script offers several ways to assign a value to a variable. The simplest is the regular assignment (=), but assignments with operations are also supported: 4. What are the Characteristics of the functions?
4. 4. Characteristics of the functions are The characteristics of the functions in WML Script are mentioned below Function declarations cannot be nested. Function names must be unique within one compilation unit. All parameters to functions are passed by value. Function calls must pass exactly the same number of arguments to the called function as specified in the function declaration. Function parameters behave like local variables that have been initialized before the function body (block of statements) is executed. A function always returns a value. By default, it is an empty string (" "). However, you can use a return statement to specify other return values. A function in WMLScript is defined using the following format. The parts enclosed inside brackets [] are optional. [extern] function function_name ([argument1, argument2...])
5. 5. { WMLScript statements here [return (some_value);] The extern keyword The extern keyword is used to specify that a function can be called from both inside and outside of the WMLScript file, i.e. the function can be called from functions in the same WMLScript file, from functions in a different WMLScript file, or in a WML file. If you define a function without the extern keyword, the function can only be called from functions in the same WMLScript file. WMLScript function Arguments Arguments are used to pass values into a function. Unlike programming languages like C++ or Java, WMLScript does not require you to specify the data type of an argument. For example, to pass two numbers into
6. 6. the WMLScript function wmlscript_function(), you will define something like this: function wmlscript_function (number1, number2) { ... } If a function does not require any arguments, you still need to include the parentheses (), like this: unction wmlscript_function () { ... }
7. 7. The return statement The "return (some_value);" statement is used to return a value back to the calling function in WMLScript. For example, the calculateSum() function below returns the sum of two numbers back to the calling function each time it is executed: function calculateSum(number1, number2) { return (number1 + number2); } The wmlscript_function() function below calls calculateSum() with two arguments 1 and 2. The value 3 is returned from calculateSum() and is assigned to the sum variable:
8. 8. function wmlscript_function() { ... sum = calculateSum(1, 2); ... } It is not compulsory to include a return statement in a WMLScript function. If no return statement is included, the default value, which is an empty string, will be returned. 5. Which are the library functions that handle absolute URLs? Explain. Isvalid, getScheme, getHost, getPort, getPath are some of the
9. 9. functions which handles absolute URLs This library contains a set of functions for handling absolute URLs and relative URLs. The general URL syntax supported is: ://< host > :< port >/ < path >; < params>? #< fragment> The following functions: loadString ,unescapeString ,escapingString, resolve,getRefer ,getBase ,getFragment ,getQuery ,getParameters ,getPath ,getPort ,getHost ,getScheme and isValid which comes under URL Library is discussed in this section isValid Function : isValid(url) Description : Returns true if the given url has the right URL syntax, otherwise returns false. Both absolute and relative URLs are supported. Relative URLs are not resolved into absolute URLs.
10. 10. Parameters : url=String Return value : Boolean or invalid. : Exceptions Example : vara=URL.isValid(http://www.webcomtec.com/script#func()); II a = true var b = URL.isValid("../common#test()"); II b = true Varc= URL.isValid("experimental?://www.webcomtec.com/pub") II c = false getScheme Function : getScheme (url) Description : Returns the scheme used in the given url.
11. 11. Both absolute and relative URLs are supported. Relative URLs are not resolved into absolute URLs. Parameters : url=String Return value : String or invalid Exceptions : if an invalid URL syntax is encountered while extracting the scheme, an invalid value is returned. Example : Var a = URL.isValid(http://w.a.com"); //a = "http" Var b = URL.getScheme("w.a.com"); II b = . "" getHost Function : getHost(url) Description : Returns the host specified in the given url. Both absolute and relative URLs are supported. Relative URLs are not resolved into absolute URLs. Parameters : url=String
12. 12. Return value : String or invalid Exceptions : If an invalid URL syntax is encountered while extracting the host part, an invalid value is returned. Example : var a= URL.getHost("http://www.webcomtec.com/pub"); II a = "www.webcomtec.com" var b = URL.getHost(".path#frag") ; II b = " " getPort Function : getPort(url) Description : Returns the port number specified in the given url. If no port is specified, an empty string is returned. Both absolute and relative URLs are supported. Relative URLs are not resolved into absolute URLs. Parameters : url=String Return value : String invalid
13. 13. Exceptions : If an invalid URL syntax is encountered while extracting the port number, an invalid value is returned. Example : var a = URL.getport(http://www.webcomtec.com:80/path"); II a= "80" var b = URL.getport("http:/www.webcomtec.com/path"); II b = "" getPort Function : getPort(url) Description : Returns the port number specified in the given url. If no port is specified, an empty string is returned. Both absolute and relative URLs are supported. Relative URLs are not resolved into absolute URLs. Parameters : url=String Return value : String invalid Exceptions : If an invalid URL syntax is encountered while extracting the
14. 14. port number, an invalid value is returned. Example : var a = URL.getport(http://www.webcomtec.com:80/path"); II a= "80" var b = URL.getport("http:/www.webcomtec.com/path"); II b = "" getPath Function : getPath(url) Description : Returns the path specified in the given url. Both absolute and relative URLs are supported. Relative URLs are not resolved into absolute URLs. Parameters : url=String Return value : String or invalid. Exceptions : If an invalid URL syntax is encountered while extracting the path, an invalid value is returned.
15. 15. Example : var a= URL.getpath(http://w.a.com/home/sub/comp#frag"); II a = "/home/sub/comp" var b = URL.getPath("../home/sub/comp#frag"); II b = "../home/sub/comp" getParameters Function : getParameters(url) Description : Returns the parameters used in the given url. If no parameters are specified an empty string is returned. Both absolute and relative URLs are supported. Relative URLs are not resolved into absolute URLs. Parameters : url = String Return value : String or invalid. Exceptions : If an invalid URL syntax is encountered while extracting the
16. 16. parameter, an invalid value is returned. Example : var a = URL. getParameters("http://w.a.c/scr;3;2?x=1 & y=3"); // a = " 3 ; 2" var b = URL.getParameters ("../scr;3;2?x=1&y=3") ; II b = "3;2" getQuery Function : getQuery(url) Description : Returns the query part specified in the given url. If no query part is specified an empty string is returned. Both absolute and relative URLs are supported. Relative URLs are not resolved into absolute URLs. Parameters : url = String Return value : String or invalid Exceptions : If an invalid URL syntax is encountered while extracting
17. 17. the query part, an invalid is returned. Example : var a = URL. getQuery (http://w.a.c/scr;3;2?x=1&y=3"); II a = "x = 1&y = 3" getFragment Function : getFragment(url) Description : Returns the fragment used in the given url. If no fragment is specified an empty string is returned. Both absolute and relative URLs are supported. Relative URLs are not resolved into absolute URLs. Parameters : url=String Return value : String or invalid Exceptions : IF an invalid URL syntax is encountered while extracting the fragment, an invalid value is returned. Example :
18. 18. vara=URL.getFragment("http://www.webcomtec.com/cont#frag"); II a = "frag" getBase Function : getBase(url) Description : Returns an absolute URL (without the fragment) of the current WML Script compilation unit. Parameters : Return value : String : Exceptions Example : var a= URL. GetBase ( ); getRefer Function : getRefer(url)
19. 19. Description : Returns the smallest relative URL (relative to the base URL of the current compilation unit) to the resource that called the current compilation unit. Local function calls do not change the referer. If the current compilation unit does not have a referer, an empty string is returned. Parameters : Return value : String Exceptions : Example : var base= URL.getBase( ); //base ="http://www.webcomtec.com/currrent .scr" var referer = URL.getReferer () ; //referer = app.wml" resolve Function : resolve (baseurl, embedded URL)
20. 20. Description : Returns an absolute URL from the given base URL and the embedded URL. If the embedded URL is already an absolute URL, the function returns it without modification. Parameters : baseUrl=String Embedded Url=String Return value : String or invalid Exceptions : If an invalid URL syntax is encountered as part of the resolution, invalid value is returned. Example : var a= URL.resolve II a= invalid escapingString Function : escapeString(url) Description : This function computes a new version of a string value in which special characters are replaced by a hexadecimal escape sequence (you must use a two-digit escape
21. 21. sequence of the form %xx). Parameters : String=String Return value : String or invalid Exceptions : If string contains characters that are not part of the US- ASCII character set, an invalid is returned. unescapeString Function : unescapeString (url) Description : The unescape function computes a new version of a string value in which each escape sequence of the sort that might be introduced by the URL.escapeString () function is replaced by the character it represents. The given string is unescaped as such; no URL parsing is performed. Parameters : String=String Return value : String or Invalid Exceptions : If string contains characters that are not part of the
22. 22. US- ASCII character set, an invalid is returned. loadString Function : loadString(url,content Type) Description : Returns the content denoted by the given absolute url and the content Type. The given content type is erroneous if it does not follow the following rules: You can specify only one content type. The whole string 3 must match with only one content type and you cannot have any extra leading or trailing spaces. The type must be text, but the subtype can be anything. The type prefix must be "text/" The given behaves as follows: The content with the given content Type and url is loaded. The rest of the attributes needed for the content load are specified by the default settings of the user agent. If the load is
23. 23. successful or the returned content type matches the given content Type, the content is converted to a string and returned. If the load is unsuccessful or the returned content is of the wrong content type, a scheme-specific error code is returned. Parameters : url=String ContentType=String Return value : String, integer or invalid. Exceptions : Returns an integer error code that depends on the used URL scheme if the load fails. If Http or WSP schemes are used, HTTP error codes are returned. If an erroneous content Type is given, an invalid value is returned. Example : varmyUrl = http://www.webcomtec.com/vcards/myaddr. vcf; MyCard = URL.loadString(myUrl, "text/x-vcard");