Scratch

This topic is a guide to programming programming languages. I have made QuickSilver. Another example is Skip by ScratchReallyROCKS. I will use the QuickSilver platform for this guide. So, I recommend downloading it and learning it.

Instead of telling you exactly how to make one, I'm going to give you ideas for how to solve problems like variables, repeats, etc. So, let's get started!

Chapter 1: How it all works
The biggest problem for most programming language programmers is how to get started. The easiest way is to think of a program as a list. You also need a variable called 'Line'. The basic coding then becomes:

Set Line to 1
Repeat until Line = Length of List
    Change Line by 1
    If item Line of List = {command}
        {action}
    If item Line of List = {other command}
        {other action}
    etc.

There are a few extra things (like arguments, flow control, and terminators) but we'll worry about those later.

Chapter 2: Arguments
An argument is basically an input. The (5)+(10) block takes two arguments, 5 and 10 in this case.
The best way to deal with arguments is to have each argument in a new line:

{command}
{argument 1}
{argument 2}

Now, arguments can be represented by the simple coding

(Item ((Line)+(1)) of (List))

Make sure you put in a [change (Line) by {number of arguments}] at the end.
Here's an example of how this could be used:

Set Line to 1
Repeat until Line = Length of List
    Change Line by 1
    If item Line of List = 'PRINT'
        Say (item(Line+1) of (List))
        Change Line by 1

Chapter 3: Variables
The best way to battle variables is with a list called 'variables'. Each item stands for a variable. So, you can add, edit, and use variables. But you can't name them. To name them, you need the list 'variable names'. 'Variable names' contains all the variables' names (like variables contains the values). Now, the code is

set n to 1
repeat until item n of var. names = {variable name here}
   change n by 1

item (n) of (variables) is the value of the desired variable

Chapter 4: Flow control
In Scratch, flow control is the orange control blocks. Here, the best way to use flow control is with LBL and GOTO/JMP-like commands. Here's how it works:

LABEL
loop
Say
Hi!
JMP
loop

Here, LABEL labels that line as 'loop', and JMP tells the script to jump to that line. So, the program will say Hi!, then jump back to 'llop', and say Hi! again and so on. To code this, you can use a similar structure as the variables: a list called LABELS, and one called LABEL NAMES. The only differences are that you put the line number instead of the variable and you add a

set Line to {input line # here}

at the end.

Chapter 5: Compilation [saving programs]
coming soon

Last edited by Hardmath123 (2011-04-18 12:17:03)