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1.4 Control structures

The first thing to understand about Pike is that just like any other programming language it executes one piece of code at a time. Most of the time it simply executes code line by line working its way downwards. Just executing a long list of instructions is not enough to make an interesting program however. Therefore we have control structures to make Pike execute pieces of code in more interesting orders than from top to bottom.

We have already seen an example of the if statement: 

if( expression )
    statement1;
else
    statement2;
if simply evaluates the expression and if the result is true it executes statement1, otherwise it executes statement2. If you have no need for statement2 you can leave out the whole else part like this: 
if( expression )
    statement1;
In this case statement1 is evaluated if expression is true, otherwise nothing is evaluated.

Note for beginners: go back to our first example and make sure you understand what if does.

Another very simple control structure is the while statement: 

while( expression )
    statement;
This statement evaluates expression and if it is found to be true it evaluates statement. After that it starts over and evaluates expression again. This continues until expression is no longer true. This type of control structure is called a loop and is fundamental to all interesting programming.

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