WMLScript Data Types

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Like JavaScript, WMLScript is weakly typed. WMLScript has only one type of variable, which is var. However, WMLScript variables are actually handled as five primitive data types internally. A variable can be used to store a value of any of the five primitive data types. The data types supported in WMLScript are:

1. Boolean. A Boolean value can be true or false.


var variable1 = true;
var variable2 = false;

2. Integer. WMLScript uses 32-bit integers with two's complement. This means an integer value can be in the range from -232/2 to 232/2-1, i.e. -2147483648 to 2147483647.


var variable1 = 10000;
var variable2 = -10000;

3. Float. WMLScript uses 32-bit single precision format to represent floating-point numbers. The maximum value supported is 3.40282347E+38. The smallest positive nonzero value supported is 1.17549435E-38. Note that some mobile devices do not support floating-point numbers. The float() function of WMLScript's Lang standard library can be used to check whether a mobile device supports floating-point numbers.


var variable1 = 11.11;
var variable2 = -11.11;

4. String. A string contains some characters.


var variable = "WMLScript Tutorial";

5. Invalid. This is used to indicate that a variable is invalid.


var variable = invalid;

Sometimes the result of an operation is of the invalid type. This means errors have occurred during the operation. One example is the divide-by-zero error:

var variable = 100 / 0;

After the execution of the above script, variable contains the invalid value. You can use the isvalid operator to find out whether a variable is of the invalid data type. It will be covered shortly in this WMLScript tutorial.

The data types of operands determine the action of an operator. For example, + is both the addition operator and the string concatenation operator. If the operands of the + operator are numeric values, the addition operation will be done. For example, the result of 10+15 is 25. If any operands of the + operator are of the string data type, the string concatenation operation will be done. For example, the result of "10"+"15" is "1015". The WMLScript interpreter will carry out a data type conversion automatically if necessary. For example, if the WMLScript interpreter encounters the operation 10+"15", the numeric value 10 will first be converted to the string data type. After that the string concatenation operation will be performed. The result will be "1015".

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