AST in JSON format

Brendan Eich brendan at mozilla.com
Mon Dec 7 18:34:13 PST 2009


On Dec 7, 2009, at 4:07 PM, Oliver Hunt wrote:

> <snip>
>
>> OTOH, if we standardize an AST format, then presumably we'll be  
>> adding
>> a source->AST API function that uses the implementation's existing  
>> parser.
>
> I'd be worried about assuming that this is an obvious/trivial thing  
> for implementations to do, you're effectively requiring that the  
> internal AST representation of an implementation be entirely  
> standardised.  For example it is not possible for JSC's parser to  
> produce an AST that exactly matches the input code -- I would expect  
> similar problems with other implementations.

This is a good point, we've talked here before about bottom-up vs. top- 
down parser trade-offs, left- vs. right-associativity for && and ||,  
etc.

Also, some (at least Waldemar, IIRC) on TC39 have objected to  
intermediating concrete syntax to semantics via an AST, since it  
increases the size and complexity of the standard.

/be



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