Declare many variables which have the same type just in one line?

[littlewhitecloud]

I have noticed that when declaring variables in jou, we need to use a lot of lines which is unnecessary.

ax:int
ay:int
bx:int
by:int
...

So should we create a syntax to combine them into just one line?

[Akuli]

I think we could add syntax like x, y, z: int. It would be similar to int x, y, z; in C. This syntax would be useful/convenient, but there is a problem with it.

Usefulness: At first I thought we don't need this because Python doesn't have it, but Jou needs this more than Python. For example, consider the following code, taken from last year's AoC solutions:

x: long
y: long
z: long
dx: long
dy: long
dz: long
assert fscanf(f, "%lld, %lld, %lld @ %lld, %lld, %lld\n", &x, &y, &z, &dx, &dy, &dz) == 6
result[i] = MovingPoint{start = [x,y,z], speed = [dx,dy,dz]}

In Python, I would probably do this instead:

x, y, z, dx, dy, dz = map(int, re.findall("-?\d+", line))
result.append(MovingPoint(start=(x, y, z), speed=(dx, dy, dz))

Problem: What should the following do? Is x set to 123 or is it uninitialized/undefined?

x, y: int = 123

If x is set to 123, then without the type annotation this would be x, y = 123. This looks like unpacking in Python, so it's just confusing and bad.

If x is uninitialized/undefined, this will confuse people who don't know it. They will write x,y,z: int = 0 and think that all variables are zero, and now their program contains UB and they wonder why it behaves weirdly. (This happens in C.)

[Akuli]

It's tempting to add [x, y, z]: int[3], but I think it's not as simple as Jou code should be.

[Akuli]

I think:

• x, y: int should be supported
• x, y = 0 should fail with error cannot assign to multiple comma-separated variables
• x, y: int = 0 should fail with error cannot assign to multiple comma-separated variables

@littlewhitecloud What do you think?

[littlewhitecloud]

I think:

• x, y: int should be supported
• x, y = 0 should fail with error cannot assign to multiple comma-separated variables
• x, y: int = 0 should fail with error cannot assign to multiple comma-separated variables

@littlewhitecloud What do you think?

I agree.

Is there a syntax for assign multiple variables like this?

x = y = 0

If so, I think we should raise error like this:

x, y: int = 0 -> cannot assign to multiple comma-separated variables with a single value, try to use syntax like this: x = y = 0

[Akuli]

Is there a syntax for assign multiple variables like this?

x = y = 0

I thought so, but turns out there isn't. It can be added later if needed.