Amaury Forgeot d'Arc amauryfa at gmail.com
Fri Jun 28 19:01:47 CEST 2013

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2013/6/28 Pynix Wang <pynix.wang at gmail.com>

> I want use coffeescript function syntax to write python lambda expression
> so I modified the Grammar file.
>
> ```
> atom: ('(' [yield_expr|testlist_comp|vararglist] ')' |
>        '[' [testlist_comp] ']' |
>        '{' [dictorsetmaker] '}' |
>        NAME | NUMBER | STRING+ | '...' | 'None' | 'True' | 'False')
> trailer: '(' [arglist] ')' | '[' subscriptlist ']' | '.' NAME | '->' text
> ```
>
> but when I write
> ```
> (x,y=1)->x+y
> ```
> the parser doesn't go into vararglist.
>

This grammar is not LL(1) anymore (it's probably LALR now)
when seeing "x", it has the choice between testlist_comp and vararglist,
and the first one is picked.
Python's parser generator only supports LL(1) grammars.

-- 
Amaury Forgeot d'Arc
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