Discuss Scratch

squelz
Scratcher
35 posts

Pls explain lists to me

im just working on a project for free time and idk how to use lists
96498cb
Scratcher
100+ posts

Pls explain lists to me

uh so basically they are a list of things that you can use for like inventory and custom x & y games
EpicGhoul993
Scratcher
1000+ posts

Pls explain lists to me

For basic information, I recommend reading the Scratch Wiki. Here is the article about lists.
deck26
Scratcher
1000+ posts

Pls explain lists to me

Imagine you wanted to draw a shape but didn't know how many sides it had but wanted it to have up to 8 sides. You don't want to have to store 8 x-values and 8 y-values all in different variables as that would be hard to keep track of. Even harder if you wanted to ba able to remove one vertex and replace it with a new one in a different position so, for example, the fourth point is now the third, the fifth is the fourth and the new point is the new fifth point.

With a list of x values you can store as many x values as you want. A corresponding list would store the y-values. Now if the third pont is removed you just remove the third items from both lists. The lists now contain one item fewer and you can insert a new value at the fifth position in each list to replace it (if required).

You can then draw the shape by using a loop

go to item 1 of x-list, item 1 of y-list
pen down
set var1 to 2
repeat until var1 > length of x-list
go to item var1 of x-list, item var1 of y-list
change item1 by 1
end repeat loop
go to item 1 of x-list, item 1 of y-list
pen up

That simple loop will draw a triangle or a square or a pentagon or whatever - it just depends how long the list is.

That's just one example but shows how useful a list can be to handle multiple values.

Last edited by deck26 (Feb. 11, 2025 15:52:37)

squelz
Scratcher
35 posts

Pls explain lists to me

so what can lists be used for in making a game? and is it possible to have a projectile go to a clone of another sprite

Last edited by squelz (Feb. 11, 2025 19:17:06)

GameCatastrophe0927
Scratcher
1000+ posts

Pls explain lists to me

squelz wrote:

so what can lists be used for in making a game? and is it possible to have a projectile go to a clone of another sprite
Lists can be used for saving large amounts of data, turning multiple numbers into one larger number, scanning strings letter-by-letter, storing prices, and a lot of stuff like that.
souleymane2
Scratcher
100+ posts

Pls explain lists to me

squelz wrote:

is it possible to have a projectile go to a clone of another sprite

if you save every position of the clones in a list you can indeed achieve this.

Assign every clone an ID value (as a number) and create two list.

Every clone will then edit its id value to its current position like so:

replace item (clone#) of [clone x v] with (x position)
replace item (clone#) of [clone y v] with (y position)

Then to have a projectile move to the 4th clone for example you just have to move it to the 4th positions like so:

glide (1) secs to x: (item # of [4] in [clone x v]) y: (item # of [4] in [clone y v])
squelz
Scratcher
35 posts

Pls explain lists to me

can i get an example of this being used in a game
kyoufu_gaaden
Scratcher
85 posts

Pls explain lists to me

If you know what variables are, they are basically capable storing several variables at once. They are like banks of info.
deck26
Scratcher
1000+ posts

Pls explain lists to me

squelz wrote:

can i get an example of this being used in a game
Any particular use of lists or just any?

https://scratch.mit.edu/projects/46472058/ uses lists for the x and y positions of the clones.

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