If, else and while

while (boolean __condition) { }
if (boolean __condition) { } else { }

Description

Is used for the control structures. You can also take a look at foreach().

if, else

Executes the code block following the statement if condition evaluates to true. Executes the code in the (optional) else statement otherwise. The code following one of the statements has to be enclosed in curly brackets, except for else when else if is used together.

while

Same as above, except that after execution the statement is always evaluated again and the code block re-executed accordingly. There is no else after a while loop.

Example

Executing the following code:

use System;
var testvalue = 3;

if (testvalue > 2) {
    System.print("Testvalue is larger than 2.");
} else {
    System.print("Testvalue is not larger than 2.");
}

will print:

Testvalue is larger than 2. 

The next example is a possible use of a while loop.

while(i<file_count) {
processNextFile();
i += 1;
}

More than two cases

You can use multiple if clauses in succession:

if ( ... ) { 
    ...
} else if ( ... ) {
    ...
} else if ( ... ) {
    ...
} else {
    ...
}

The combination else if makes sure that never more than one block is executed, and you don't have to nest consecutive if blocks, which is important.