const and/or var

[satyr]

const

Performs a series of assignments and flags the variables as read-only.

const a = 0, b = 1
...
a = 2  # compile error

var

Avoids awakward a = b = void.

var a, b

[paulmillr]

const is a pretty awesome idea if it'll be compile time. 👍

[michaelficarra]

Yes, assignment is horrible. But you won't be able to enforce this statically when the constants are members of the global scope. Is that an acceptable inconsistency?

[satyr]

when the constants are members of the global scope

Global variables are read-only already:

$ coco -e '++Math'
SyntaxError: increment of undeclared variable "Math" on line 1

[michaelficarra]

$ node
> var a = 0
undefined
> this.a
0
> this.a = 1
1
> a
1
> 

You can't statically catch those assignments.

[satyr]

You can't statically catch those assignments.

Don't have to.

• this.a is not a variable.
• Coco can't declare global variables (or pretends so in case of --bare).

[michaelficarra]

Exactly. When --bare is used, top-level "consts" are re-assignable through a reference to the global object. Are you willing to ignore that case? If I saw that a language had a "constant" feature, I would hope that it could guarantee that the value would never change, regardless of environmental factors like what flags were used when the program was compiled.

[satyr]

Are you willing to ignore that case?

Yes. --bare is for cases where the IIFE wrapper is redundant (like node modules) and never for creating globals.

[michaelficarra]

That's reasonable.

[paulmillr]

@michaelficarra would you consider this (at least const) for coffee-redux?

[michaelficarra]

@paulmillr: Absolutely not. The goal of CoffeeScriptRedux is to be feature-compatible with CoffeeScript, with no feature additions besides those listed on the kickstarter page. Once it reaches that state, I plan to fork it and add cool features (like const) that I've enumerated at coffee-of-my-dreams, many of which are already available in LiveScript.

[paulmillr]

ah, that's even cooler. then it will be truly drop-in replace. nice to hear.