Re: ! function

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From	"Christoph M. Becker" <cmbecker69@arcor.de>
Newsgroups	comp.lang.javascript
Subject	Re: ! function
Date	Thu, 07 May 2015 23:27:37 +0200
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Evertjan. wrote:

> "Christoph M. Becker" <cmbecker69@arcor.de> wrote on 07 mei 2015 in 
> comp.lang.javascript:
> 
>>  to enforce an expression context.
> 
> No "expression context" [I hope you mean 'scope'] is forced,
> the return value is just accepted as required.

No, I don't mean "scope".  I was referring to *parsing*; however, the
term "expression context" might be misleading.

> But why does this work:
> 
> -function(a){alert(a);return 2}('hi')
>
> and this does not:
> 
> function(a){alert(a);return -2}('hi')
> 
> ??

This is a syntax issue.  See annex A of ECMA-262 5.1 Edition[1].  The
first line is parsed as (simplified)

  SourceElement -> Statement -> Expression -> UnaryExpression -> -
UnaryExpression -> - FunctionExpression Arguments -> ...

while the second line is parsed as (again simplified)

  SourceElement -> FunctionDeclaration -> ...

and the remaining ('hi') is a syntax error, as no ASI applies here.

[1] <http://www.ecma-international.org/ecma-262/5.1/#sec-A>

-- 
Christoph M. Becker

Thread

! function Andrew Poulos <ap_prog@hotmail.com> - 2015-05-07 20:15 +1000
  Re: ! function "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-05-07 13:04 +0200
  Re: ! function "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2015-05-07 05:02 -0700
  Re: ! function Joao Rodrigues <groups_jr-1@yahoo.com.br> - 2015-05-07 12:27 -0300
    Re: ! function JJ <jj4public@vfemail.net> - 2015-05-08 00:09 +0700
    Re: ! function "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-05-07 21:07 +0200
      Re: ! function "Christoph M. Becker" <cmbecker69@arcor.de> - 2015-05-07 21:31 +0200
        Re: ! function "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-05-07 22:20 +0200
          Re: ! function "Christoph M. Becker" <cmbecker69@arcor.de> - 2015-05-07 23:27 +0200
            Re: ! function "Christoph M. Becker" <cmbecker69@arcor.de> - 2015-05-08 00:26 +0200
              Re: ! function "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-05-08 11:00 +0200
                Re: ! function James Lewis <lewisje@gmail.com> - 2015-06-05 09:10 -0700
          Re: ! function Scott Sauyet <scott.sauyet@gmail.com> - 2015-05-18 13:31 -0700
            Re: ! function "Christoph M. Becker" <cmbecker69@arcor.de> - 2015-05-19 01:39 +0200
              Re: ! function Scott Sauyet <scott.sauyet@gmail.com> - 2015-05-19 05:48 -0700
        Re: ! function Joao Rodrigues <groups_jr-1@yahoo.com.br> - 2015-05-07 17:47 -0300
          Re: ! function "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-05-07 23:22 +0200
            Re: ! function Joao Rodrigues <groups_jr-1@yahoo.com.br> - 2015-05-07 19:08 -0300
              Re: ! function "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-05-08 12:08 +0200

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