Scratch

....::::Scratch programming tricks::::....

Hello everyone!

I would like to help new people to improve their programs, so I decided to create this topic.
You can find some programming tricks in here (isn't that what the title's saying?  )

1. Smoother movement

You can let a sprite move using several different scripts, but which one is the best? You can use this block:
[blocks]
<when[  ]key pressed>
[/blocks]
or this one:
[blocks]
<forever>
   <if><key[  ]pressed?>
   <end>
<end>
[/blocks]

I always use the second, it is uhm... smoother! I can't really explain the effect of the first one, but you can try it out yourself. Open a text editor, and press the same key a few seconds. You see? The letters don't come in with the same difference in time, it is slower at the beginning. It will be the same with your Scratch program. The second option also has another + : you only need one script for your movement, in stead of 1 script/key.


2. Changing a variable between 1 and 0 - toggling

Again, there are several ways to do it. You can use this:

[blocks]
<when I receive[ change
<if> variable = 1
   <set{ variable }to( 0
<else>
   <set{ variable }to( 1
<end>
[/blocks]

But you can do it shorter!
[blocks]
<when I receive[ change
<set{ variable }to( (( 1 <-> variable ))
[/blocks]

Get it? when variable is 1   ==> 1 - 1 = 0
when variable is 0 ==> 1 - 0 = 1
It will toggle!


3.A Switching a variable between positive and negative
Switching a number between positive and negative is very easy:

[blocks]
(( <{ variable1 }> <*> -1 ))
[/blocks]

3.B Switching a variable to a negative value
The example will "toggle" a number between positive and negative. If you want it to be only positive, use the "abs" formula (from the math block) Ofcourse it should have to be easy to turn a number always to a negative value, if you see 3.A.

[blocks]
(( <abs( <{ variable1 }> <*> -1 ))
[/blocks]


4. Floor function
(Bit more advanced)
Sometimes you don't want to round to the nearest integer (.4 => 0 and .5 => 1), but you want to round to the nearest lower integer. This is called the "floor" function in a lot of languages. Scratch does not supports this in the math block yet, but there is an easy way around it.

[blocks]
   <round(  (( <{ variable1 }>    <-> 0.5 ))
[/blocks]

I will add some other tips soon!

Note: This is just a list of programming tricks, and i do not have created them all myself. I only thought it would be nice to have them together in a list.

Last edited by JSO (2008-04-07 11:16:26)