LOOPs and FOR loops
LOOPs
Loops are a very basic and necessary part of Turing, as well as any programming language. To be able to use loops, first we must understand the syntax.
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loop |
| code: |
end loop |
Simple enough? I thought so
. Now that we know the basic syntax we can understand what a loop does.
A loop simply executes the code between the "loop" and the "end loop" forever.
Question A.) Try making your own loop that outputs "Turing rocks!" over and over.
(answers are found at the bottom of the tutorial)
So what's the point of making something repeat over and over forever? Well, it doesn't have to go on forever.
Cervantes wrote:
A loop simply executes the code between the "loop" and the "end loop" forever.
I'm sorry I kinda lied
the loop will only exit if there is an exit statement inside it.
EXIT statements
SYNTAX:
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exit |
difficult huh? well, what's it do already?! Agreed, what does it do? By looking at the syntax of the word you can assume that it exits something. You'd be right if you assumed that! But what does it exit? What have we been talking about all this time? That's right!! It exits a loop! Of course, there is little point to simply putting "exit" in a loop if it has no parameters. In other words, 'exit' is usually accompanied by the command "when"
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exit when number = 1 |
that code will, if placed inside a loop, exit the loop when the variable called number is equal to 1. Where does it go when it exits the loop? It goes 1 line after wherever the closest "end loop" is.
For this next problem you're going to need a counter. A counter is a variable that you make that increases by a set incremiment every time something happens.
Question B.) Write a program that counts to 10. (No, that doesn't involve 10 put statements)
So we now know a good deal about the structure of loops.
"But Cervantes!" you ask, "when would we ever use a loop?!"
I hear you! Loops are used in pretty much every program. Think of a game, for example. You want to run the game until someone dies. That would involve a loop! Very few programs don't use loops... or for statements.
FOR loops
a for loop is very similar to a loop. The difference is that a for loop exits itself after a set number of repititions. You can, however, exit a for statement prematurely using the same "exit" line as in loops.
SYNTAX: the syntax of a for statement is more complicated then that of a loop.
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for counter : 1 .. 10 |
that is the code that will begin your for loop. However, many things can be changed about that. the "counter" can be changed to whatever you want. So can the two numbers.
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end for |
simple enough ending, yes?
"What does this all mean? What's that colon and 2 periods for? I don't understand?!"
Allow me to explain: The above for loop, when put together, will look like this
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for counter : 1 .. 10 end for |
This for loop will execute the code between the "for counter : 1 .. 10" and the "end for" 10 times. Unfortunately, there is no code there
. It will also keep track of howmany times it has gone repeated, using the variable "counter". You don't have to declare "counter" with a previous "var counter : blah blah blah" line.
Question C.) Write a program using a for loop that will count from 1 to 15.
NOTE: you don't have to have a counter like you had in question B.). the for loop does the counting for you
There are some other funky things that you can do with the for loops. You can make them count backwards, or by a different incriment. to do this:
COUNT BACKWARDS
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for decreasing counter : 10 .. 1
end for |
COUNT by a different INCRIMENT
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for counter : 1 .. 11 by 2
end for |
neat huh? You can even combine these two!
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for decreasing counter : 11 .. 1 by 2
end for |
"When would you ever use a for loop?!"
For loops are often found inside a loop. For loops work very well with arrays, but we don't want to go there just yet. In due time
Now for some problems:
Question D.) Write a program that will count backwards from 64 to 1 by 3
Question E.) Write a simple game where you move a circle around the screen.
"Cervantes!! are you nuts?!" you scream.
Not really. Now that you have an understanding of loops and for loops there's only one thing holding you back from making that game! (check out the answer below)
ANSWERS
A.)
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loop
put "Turing Rocks!" end loop |
B.)
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var counter : int
counter := 0 loop counter := counter + 1 put counter exit when counter = 10 end loop |
C.)
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for counter : 1 .. 15 put counter end for |
D.)
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for decreasing counter : 64 .. 1 by 3
put counter end for |
E.) The only thing holding you back from making this game is 'Input.KeyDown" . its not hard to learn. My advice: don't try to understand why the variable for the keys is "array chars of boolean". Simply use it. You'll understand soon enough
http://www.compsci.ca/v2/viewtopic.php?t=114
^^^ = tony's super duper Input.KeyDown tutorial!
http://www.compsci.ca/v2/viewtopic.php?p=1586
^^^ = tony's super duper Loop tricks tutorial (faking goto line)
If you don't understand loops, for loops, or Input.KeyDown, PM me and I'll try to help you.
And it's awesome how you got questions/answers to solidify understanding and links to other related tutorials 
