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From: "Christoph M. Becker" <cmbecker69@arcor.de>
Newsgroups: comp.lang.javascript
Subject: Re: ! function
Date: Tue, 19 May 2015 01:39:57 +0200
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To: Scott Sauyet <scott.sauyet@gmail.com>
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Scott Sauyet wrote:

> Evertjan. wrote:
>
>> Christoph M. Becker wrote 
>>
>>> That's wrong.  According to ES 5.1 the line can't be parsed as
>>> FunctionDeclaration, because the Identifier is missing.  Actually, the
>>> code doesn't match any production, and as such is syntactically invalid.
>>
>> Quite, but that doesn't explain why
>>
>> !function(a){alert(a)}('ho');
>> +function(a){alert(a)}('ho');
>> -function(a){alert(a)}('ho');
>>
>> ... do not throw an error.
>>
>> "syntactically invalid" is just "according to the rules",
>> "throwing an error" is what should concern us in practice.
> 
> Ok, so we'll try to simplify a bit:

<snipped the story of Parry Parser and his colleagues>

A wonderful story – thanks for telling, Scott.  And a really fine
explanation of the interaction of parsers and scanners (aka
lexers/tokenizers).

Actually, I would like to see the story in a FAQ note.  Maybe chapter 4,
Function, should be augmented by a section about "Why is there an
operator before `function`?" (or similar), which explains the issue
shortly, and links to the full story.

Thoughts?

-- 
Christoph M. Becker