An array destructing specification choice

Claus Reinke claus.reinke at talk21.com
Sat Nov 12 00:48:19 PST 2011


> Embedded spreads is already in the ES6 draft for  both array literals
> and argument lists.  I'm not at all sure that embedded rests in
> destructurings are such a good idea.  Just to start with, what does this 
> mean:
>
>   [a,b,...r,c,d = [1,2,3]
>
> ..
> This sort of destructuring is not real pattern matching. ..

I think this is the important point. Many of us who like "destructuring"
are still being mislead by the name, and by our experience with proper
pattern matching constructs.

- please rename the current state to "selection shorthand"
- no matter the name, the differences between construction
    and deconstruction cannot be good

Btw, I've known at least one language where one could write

[...,['key',value],...] = some_dictionary_array

to get key-value lookups. Again, this depends crucially on proper
pattern-matching semantics (this used match failure and fallback
within a single pattern), even though it is "just" a lhs variant of
what is permitted as on the rhs.

By specifying only a simplified form of selection shorthand, while
occupying the syntactic grounds belonging to pattern matching,
we are moving on shaky ground.

Claus
http://clausreinke.github.com/
http://clausreinke.github.com/js-tools/

 



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