Suggestion: Support multiple assignment

[macabeus]

Some languages, such Python, Swift, Lua and JS, support multiple assignment. For example:

# Python and Lua
a, b = 1, 2

// Swift
let (a, b) = (1, 2)

// JS
let [a, b] = [1, 2]

In Wren, I think that

var a, b = [1, 2]
c, d = [3, 4]

should be a syntax sugar for

var a = 1
var b = 2
c = 3
d = 4

It is useful to add it in Wren, especially to handle function with multiple returns:

var someValue = "key:value"
var key, value = someValue.split(":")

instead of

var someValue = "key:value"
var result = someValue.split(":")
var key = result[0]
var value = result[1]

Edge case

What to do if have a different mount on right and left side? Each language have a different behavior:

// Swift
let (a, b) = (1, 2, 3) // Will crash
let (a, b, c) = (1, 2) // Will crash

# Python
a, b = 1, 2, 3 # Will crash
a, b, c = 1, 2 # Will crash

# Lua
a, b = 1, 2, 3 // a is 1 and b is 2
a, b, c = 1, 2 // a is 1, b is 2 and c is nil

// JS
let [a, b] = [1, 2, 3] // a is 1 and b is 2
let [a, ...b] = [1, 2, 3] // (using spread operator) a is 1 and b is [2, 3]

let [a, b, c] = [1, 2] // a is 1, b is 2 and c is undefined
let [a, b, ...c] = [1, 2] // (using spread operator) a is 1, b is 2 and c is []

I don't know what the ideal behavior to use in Wren. Each way has a different advantage:

• Swift and Python has the safest way.
• Lua has the simplest and easy way.
• JS has the most versatile way, but also is the most complex to implement and understand.

Assignment and Setter

Wren has assignment for variables and setter for property. What to do in this situation?

var foo, person.age = [100, 74]

[mhermier]

I don't think it is feasble as this, and would require a LOT of plumbing. In addition there is an ambiguity if you consider: var a, b = [1, 2, 3] what should be the value of b ? 2 or [2, 3] then it make ambigus: var a, b = [1, 2] since it should make b equals to either 2 or [2] Anyway if we consider var a = [1] to still be valid then the only sane consideration is to make: var a, b = [1, 2, 3] with b = [2, 3] which deafeat the purpose of your suggestion ...

I agree it is nice to have support for multiple return values, but not with this syntax.