Loops and Arrays

Loops:

• Imagine that you wanted a script to perform the same routine over and over again 50 times in a row.
• An example could be if you wanted a script to produce a table comparing temperatures in Fahrenheit and Celsius. The script should produce 50 lines in a table showing different temperatures according to the two scales.
• Instead of adding 50 almost equal lines in your script you could use loops to make the script perform a task like this. 
• There are two different kinds of loops: for and while.

For-Loop:

• The for-loop is used when you know in advance how many times the script should perform the similar task.

Syntax:

for (variable=startvalue; variable<=endvalue; variable=variable+incrementfactor) 

{

// Here goes the scriptlines you want to be looped.

};

• Enter a variablename where it says variable.
• Enter the startvalue of the loop where it says startvalue.
• Enter the endvalue of the loop where it says endvalue.
• Enter the factor each loop should increment where it says incrementfactor.

Note: The increment factor could be negative if you wanted.

Furthermore the <= could be any comparing statement.

Eg. >, == or whatever.

Example:

• In the example above it would be if you wanted it to create exactly 50 lines. 
• You would simply tell the script to loop the same lines 50 times in a row.

While-Loop:

• The while-loop is used when you don't know in advance how many times the loop should be performed. 
• You simply want the loop to be performed until a certain condition becomes true.
• 
  

Syntax:

while (variable<=endvalue) 

{

// Here goes the scriptlines you want to be looped.

}

• Enter a variablename where it says variable.
• Enter the endvalue of the loop where it says endvalue.

Note: The <= could be anything that would fit the purpose eg. >, == or whatever.

Example:

• In the example above it would be if you wanted to make a table comparing Celsius and Fahrenheit, stepping 15 degrees for each row, and you wanted the table to contain values up to say 1200 degrees of Celsius. 

Arrays:

• When working with more complex scripts you might face a situation in which you would have many more or less similar variables.
•  Instead of being forced to write a line for each operation done to such a variable, you can use arrays to help you automatize the process.

Consider this example:

Example I	Example II
value1=10;  value2=20; value3=30; .... here would go 96 similar lines .... value100=1000 ------------------------------------------------- you would need to enter 100 lines to perform an operation on your variables.	value=new Array; for (number=1;  number<=100; number=number+1) { value[number]=number*10}; ---------------------------------------------- you only need to enter 3 lines no matter how many variables you have.

• To use variable-arrays you need to define the array before referring to any of the variables in it.

This is done using the syntax: variablename=new Array;
Replace variablename with the varible you want to work as an array.

• As the example shows arrays becomes extremely powerfull when used in combination with loops.
• However you do not have to handle array-variables in loops. 
• Single variables can be addressed with a syntax like this:value[9]=170;