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Re: Convert string to C expression syntax

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On 11/09/2013 23:27, James Kuyper wrote:
> On 09/07/2013 12:25 AM, Paul D. DeRocco wrote:
>>   > On 7/30/2013 7:58 PM, nilay wrote:
>>   >
>>> I want to do the following,
>>>
>>> ==========================================
>>> int main(int argc, char *argv[])
>>> {
>>>
>>>       ...
>>>       ...
>>>       if (*argv[1])
>>>       {
>>>         ...
>>>       }
>>>
>>>       ...
>>> }
>>> ==========================================
>>>
>>> as i tried to show above, I want to pass a filter condition
>>> at command-line input. And I want to convert that input string
>>> to 'if-condition expression' so that it can be used in the program.
>>> How can it be done?? I am struggling very hard to get it right.
>>
>> You can't do this in C. If you want to do stuff like this, you should
>> take up Python instead.
>
> You can't do this that way in C, nor in any other simple way. It might
> be simpler to do it in Python, but it certainly can be done in C. You
> just need to write code for parsing the condition expression, and then
> evaluating it. If the condition expression has a very simple syntax,
> that's trivial to do. However, even if he wants to support the full
> complexity of a C-like syntax, it should still be feasible. Components
> (or at least, design ideas) borrowed from a C compiler should be
> adaptable to this use. C has famously been a bootstrapped language: more
> advanced versions of C were first implemented by using more primitive
> versions of C to write the compiler, so such components can certain be
> written in C.

Yes and if you are running C on an interpreter (they do exist) it comes 
about pretty naturally.

Francis
>
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Convert string to C expression syntax nilay <nilaybhatt@gmail.com> - 2013-07-30 21:58 -0500
  Re: Convert string to C expression syntax James Kuyper <jameskuyper@verizon.net> - 2013-07-31 21:22 -0500
  Re: Convert string to C expression syntax Barry Schwarz <schwarzb@dqel.com> - 2013-07-31 21:22 -0500
    Re: Convert string to C expression syntax Keith Thompson <kst-u@mib.org> - 2013-08-01 12:58 -0500
      Re: Convert string to C expression syntax Ike Naar <ike@ukato.freeshell.org> - 2013-08-01 21:05 -0500
        Re: Convert string to C expression syntax Keith Thompson <kst-u@mib.org> - 2013-08-02 18:34 -0500
  Re: Convert string to C expression syntax gordonb.uvkjx@burditt.org (Gordon Burditt) - 2013-07-31 21:22 -0500
  Re: Convert string to C expression syntax Roberto Waltman <usenet@rwaltman.com> - 2013-08-05 11:24 -0500
  Re: Convert string to C expression syntax malcolm.mclean5@btinternet.com - 2013-09-02 04:09 -0500
  Re: Convert string to C expression syntax "Paul D. DeRocco" <pderocco@ix.netcom.com> - 2013-09-06 23:25 -0500
    Re: Convert string to C expression syntax James Kuyper <jameskuyper@verizon.net> - 2013-09-11 17:27 -0500
      Re: Convert string to C expression syntax "Paul D. DeRocco" <pderocco@ix.netcom.com> - 2013-09-12 11:34 -0500
      Re: Convert string to C expression syntax Francis Glassborow <francis.glassborow@btinternet.com> - 2013-09-12 11:38 -0500
  Re: Convert string to C expression syntax Nitin Tripathi <2nitintr@gmail.com> - 2013-09-11 17:31 -0500

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