The idea is a way to have local variables – not just ‘For this sprite only’ but for a script, or a specific part of a script.
This is done by adding a new block, let in:

The first say block prints ‘bar’.
The second say block will NOT say ‘bar’, as the foo variable isn't in the scope. The Scratch behaviour for undefined variables is to create a new ‘for this sprite only’ variable with the value of zero, so unless that behaviour is changed, the second say block should print zero.

Other possibilites
Instead of gray, it could be an orange variables block, like this:

It would be useful if I could declare multiple local variables in a single let block, perhaps something like

Each time you press the rightmost arrow, a new grey oval shape (but not really a reporter, as it isn't a block and can't be dragged out.) with '(variable name) be [variable value]' would appear.
Perhaps it should have an equals sign rather than ‘be’?

I personally like the ‘be’ version better.

Workaround
There is a sort-of-workaround that can achieve the same results in many cases:

Of course, it doesn't matter what the custom block is called. But this is obviously tedious and often will NOT suffice:

In this case, since ‘foo’ is local to my block 1 and my block 2 is declared outside of my block 1 foo can't be accessed. (Lambda would fix this though! Lambda fixes pretty much everything!!)

Cases when local variables are needed and there is no workaround that doesn't require hacked blocks
There are cases when doing something in Scratch is simply not possible without local variables.

Say I have a custom block, named foo, that uses the variable ‘foo i’ for counting:

This works if used on a single thread at the same time, but if two threads run this block at the same time, it'll get completely messed up.
Here's the solution, which requires hacked blocks:

This is non-trivial, requires hacked blocks (which ST doesn't super approve of), and makes the custom block annoying to use.

This example would be messed up anyway because of the same sprite switching between saying things. So I'd need to move one script to another sprite.
But as there is no such thing as ‘global custom blocks’, I'd need to use broadcasts.
The problem here is that I'd need to use a global variable to pass ‘i name’, and as the global variable isn't local to the block, I'd have the same issue all over again, except this time it's not possible to solve at all without copying the block into the other sprite!!

Please post if you support, don't support, semi-support, and your reasons why.

Can't you just use inputs as local variables?

Sigton

???

seems confusing to people who do only programming in scratch, so semi-support.

support

Sigton wrote:

Can't you just use inputs as local variables?

He could, but the problem he's addressing is the lack of mutability. That is, once you assign a value to a block argument, you cannot change it. The other way around, if you use a local variable instead, there's no way to discard it after being used.

This idea is not new to me, and it has been suggested several times in the past; nonetheless, I still support some way of incorporating temporary variables. The C-block is a nice idea and allows one to discard variables after a point in the code (unlike Snap!). Supposing it doesn't introduce anything radically new to the Scratch editor interface, it is possible to implement smoothly.

For example, if you right click ‘temp1’, you have the option to delete the variable or rename it. If you right click the block, you have the option to add a new temp variable (aptly named “temp” with an increment).

Edit: I should explain why I chose this scheme instead of Jonathan50's. I want to reduce redundancy of code. The block should not do the assignment, only the declaration. See below.

When you want to modify the variable, you do this:

And using the variables is easy. Just like custom block definitions, you drag copies directly from the declaration. In total, this fulfills declaration, assignment, mutation, access, and garbage collection. In other words, it's how variables are supposed to be.

Sigton wrote:

Can't you just use inputs as local variables?

Sigton

Inputs cannot be reassigned in Scratch. Also, who would want to declare a bunch of unnecessary parameters just to get local variables?

Also, this is a duplicate. Original: https://scratch.mit.edu/discuss/topic/20661/ (idea # 3)

I like the idea of lexical scoping in Scratch. However, I don't think the exact wording of this block ('let…') works in the Scratch metaphor. Also, what if you wanted to assign multiple variables?

Zekrom01 wrote:

seems confusing to people who do only programming in scratch, so semi-support.

I don't get it. Isn't the whole point of Scratch to learn new stuff?

fivesythe wrote:

I like the idea of lexical scoping in Scratch. However, I don't think the exact wording of this block ('let…') works in the Scratch metaphor. Also, what if you wanted to assign multiple variables?

Zekrom01 wrote:

seems confusing to people who do only programming in scratch, so semi-support.

I don't get it. Isn't the whole point of Scratch to learn new stuff?

Yes, but can't you do that in another language?

The way you described it is a bit confusing, but I do support this-

To create multiple local variables, you could just nest them-

Chibi-Matoran wrote:

Also, this is a duplicate. Original: https://scratch.mit.edu/discuss/topic/20661/ (idea # 3)

That's a different idea.

fivesythe wrote:

I like the idea of lexical scoping in Scratch. However, I don't think the exact wording of this block ('let…') works in the Scratch metaphor. Also, what if you wanted to assign multiple variables?

Another naming could work.

Sigton wrote:

Can't you just use inputs as local variables?

Sigton

Read the whole first post. I explain why it won't always work, and it's not mutable, as @Zro716 and @Chibi-Matoran. (But if you're doing Functional Programming you don't need mutation. But the other issues stop it from working.)

DaSpudLord wrote:

The way you described it is a bit confusing, but I do support this-

To create multiple local variables, you could just nest them-

Huh? Shouldn't you be able to click on the variable to rename it? I should at that to the first post.

Support. I like @Zro716's version the best, but the one in the OP is nice too.

Zro716 wrote:

Sigton wrote:

Can't you just use inputs as local variables?

He could, but the problem he's addressing is the lack of mutability. That is, once you assign a value to a block argument, you cannot change it. The other way around, if you use a local variable instead, there's no way to discard it after being used.

This idea is not new to me, and it has been suggested several times in the past; nonetheless, I still support some way of incorporating temporary variables. The C-block is a nice idea and allows one to discard variables after a point in the code (unlike Snap!). Supposing it doesn't introduce anything radically new to the Scratch editor interface, it is possible to implement smoothly.

For example, if you right click ‘temp1’, you have the option to delete the variable or rename it. If you right click the block, you have the option to add a new temp variable (aptly named “temp” with an increment).

Edit: I should explain why I chose this scheme instead of Jonathan50's. I want to reduce redundancy of code. The block should not do the assignment, only the declaration. See below.

When you want to modify the variable, you do this:

And using the variables is easy. Just like custom block definitions, you drag copies directly from the declaration. In total, this fulfills declaration, assignment, mutation, access, and garbage collection. In other words, it's how variables are supposed to be.

But it's declaring them. It isn't as clear that the block is only in the scope of the C-shape. (And the way Scheme and Haskell do it is specifying the initial value.)

Jonathan50 wrote:

DaSpudLord wrote:

Huh? Shouldn't you be able to click on the variable to rename it? I should at that to the first post.

You type the variable name into the textbox to rename it.

DaSpudLord wrote:

Jonathan50 wrote:

DaSpudLord wrote:

Huh? Shouldn't you be able to click on the variable to rename it? I should at that to the first post.

You type the variable name into the textbox to rename it.

Oh. That's what I thought. In the idea in OP then you can click on the variable to rename it.

Jonathan50 wrote:

DaSpudLord wrote:

Jonathan50 wrote:

DaSpudLord wrote:

Huh? Shouldn't you be able to click on the variable to rename it? I should at that to the first post.

You type the variable name into the textbox to rename it.

Oh. That's what I thought. In the idea in OP then you can click on the variable to rename it.

Oh yeah, that works too.

Jonathan50 wrote:

Chibi-Matoran wrote:

Also, this is a duplicate. Original: https://scratch.mit.edu/discuss/topic/20661/ (idea # 3)

That's a different idea.

Are you sure?

AonymousGuy wrote:

I think this is the better solution. How it would work is similar to custom blocks. Only the blocks inside of the C-Block could use the variables. The weird looking variables and lists that look like “+” are just a quick sketch of how the using block could create more than one variable. However, I think it should only be able to hold either variables or lists.

The inspiration for this idea came from a language I use called C#, in which you can say this:

void doStuff()
{
   using (int x)
   {
      do stuff that uses int x
   }
   do stuff that doesn't use int x
}

I think that maybe these should also have different colors, and they should use the right-click functions to get the other blocks.

Chibi-Matoran wrote:

Jonathan50 wrote:

Chibi-Matoran wrote:

Also, this is a duplicate. Original: https://scratch.mit.edu/discuss/topic/20661/ (idea # 3)

That's a different idea.

Are you sure?

AonymousGuy wrote:

I think this is the better solution. How it would work is similar to custom blocks. Only the blocks inside of the C-Block could use the variables. The weird looking variables and lists that look like “+” are just a quick sketch of how the using block could create more than one variable. However, I think it should only be able to hold either variables or lists.

The inspiration for this idea came from a language I use called C#, in which you can say this:

void doStuff()
{
   using (int x)
   {
      do stuff that uses int x
   }
   do stuff that doesn't use int x
}

I think that maybe these should also have different colors, and they should use the right-click functions to get the other blocks.

using != let
The let lets (pun not originally intended, but now it is ) you assign an initial value.