Scratch

Really you don't need a book to learn variables. Variables are simply just numbers that you can control and use to control your program. Variables are most useful for if statements and you can check the variables values to determine what script to execute. for example

If score > 1000
say "you got over 1000 points"

if score > 100
say "you got over 100 points''

if score = 0
say "You are really bad at this game"

Variables are not really confusing, what can be confusing is the ways that they are put to use. And don't worry when I started programming variables and if statements confused the hell outta me too    You will get better with practice.

A variable can also be used to determine the state of a sprite. For example, if a sprite is walking could be equal to 1, if running equal to 2 and if it's standing equal to 3. Just an example.

So it sounds as if variables help one deal with QUANTITIES.  If no ammo, you can't shoot.  If someone is walking, then it will take a long time to get somewhere.  If someone scores 5 or more points they win the game. 

Or, if there are no seconds left on the clock, then the game is over.

Or, with a variable "PeopleNumber" if there are 3 or more people, then you get CROWD behavior!  If PeopleNumber = 2, then nobody can keep a secret.

Archmage, how would you construct the phrase "if touching 'ground' grounded = 1" using Scratch blocks? 

"If" requires an insert with pointed ends.  The "=" relationship is built within an insert with ROUNDED ends.  I can build "grounded = 1" but I can't combine it with the "if" block.
IF TOUCHING |sprite4|         (....assuming Sprite4 is the ground)
.........
<(grounded) = (1)>
but I can't combine those two blocks to express THEN.

(I tried to use the "blocks" at the bottom of this form but didn't succeed. When I previewed my result it wasn't what I intended, so I'll have to learn the syntax of using the blocks in these messages.  I kinda got the blocks in there, but didn't know the syntax for filling the blank spaces with names of variables, names of sprites, and numbers....  Oh well, just another challenge....)   :-) 

I hope my verbal try made sense....

BTW, I was able to build your second set of commands.
    IF <(grounded) = (1)>
        BROADCAST |jump|

Thanks!  Larry

    P.S.  it says Smilies are on, but my typed smilies never turn into graphical ones....  yet another challenge.   :-)
    PP.S.  Even worse, when I previewed this message the messaging program substituted partial green blocks for my typed )> characters.  I don't know how to retype it to prevent that, so I hope it's comprehensible.   There must be an easier way.  Or maybe I need to find a "pre-Scratch" language!!  :-)

Last edited by Larry828 (2007-08-19 23:03:31)

btw, just put a space between the parenthesis and the bracket to make it not turn into a Scratch block, example: type ) >

Paulmedwal

Last edited by paulmedwal (2007-08-19 23:06:49)

For PAULMEDWAL and ARCHMAGE,

Thanks to you both!! 

Paul, those are both great tips!  Much appreciated!   

Archmage, thanks for the coding.  The "set" command is crucial, isn't it?!  So is putting the set command within the Forever block.  I captured your message and printed it out for future reference.   -- And the easy "jump" command is neat too.

Thanks to the contributors to this topic I can feel new neurons by the hundreds springing up in my old brain.   

Kevin, I built Archmage's scripts (plus some extras to make a small project) and late last night was watching them run.  With great satisfaction, since the variable was functioning as expected.

But I did notice the endless forever loop running constantly and wondered if there was anything I could do to revise it.  Your suggestion is right to the point.

I'm planning some experiments to see whether Scratch will hold a variable in memory once it is set, or whether it has to be constantly set one way or another.  Your suggestion offers a middle ground: invoke the variable only when a change occurs.

I've had the feeling that using variables could be very powerful (and saw variables used in some of the most impressive projects) but I got stuck trying to find a step-by-step approach to learning how they work.  It would be a good subject for a tutorial for newcomers to Scratch and programming...   Thanks!

Variables are awesome stuff, and the more varied you create them, the more stuff you can do. I am using distance, angles, 3D x, 3Dy and a save copy of every variable so that You have a 3D game that can save, it is a bit too much typing to say how to do it, but gather these up so you maybe can try out how to work it.

This was SO helpful.
THANKS!!!!!!!!!!
:-)

There are 2 sorts of variables in scratch:  ones that belong only to a specific sprite, and ones that are shared by all sprites.  When you create a new sprite, it will have access to the variables shared by all sprites, but will not have any variables of its own until you create them.

If you duplicate a sprite, then the copy will have its own variables and scripts, but changing these will not change the corresponding variables or scripts of the original sprite.

you also use variables to set the y velocity for gravity

Check my scratch cat adventure games. download em and love em. they give the best way too use variables.