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Date: Tue, 21 Feb 2017 18:54:43 +0100 (CET)
From: Julia Lawall <julia.lawall@lip6.fr>
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To: Gargi Sharma <gs051095@gmail.com>
cc: outreachy-kernel@googlegroups.com
Subject: Re: [Outreachy kernel] Coccinelle Challenge Problem 2
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On Tue, 21 Feb 2017, Gargi Sharma wrote:

> Hi,
>
> Here's my coccinelle script to parentheses around the right hand side of an
> assignment.
>
> @@ expression e, e1, e2; @@  
> e =  
> -(  
>         e1 + e2
> -)  
>  
> @@ expression e, e1, e2; @@  
> e =  
> -(  
>         e1 - e2  
> -)
>  
> @@ expression e, e1;
> contant c; @@  
> e =  
> -(  
>         e1 << c  
> -)
>  
> @@ expression e, e1;
> constant c; @@  
> e =  
> -(  
>         e1 >> c  
> -)

It looks reasonable.  I don't think you need to restrict the right side of
>> and << to constants, though.

Also, the whole thing can actually be much shorter, because there is a
"binary operator" metavariable type.  So you could say:

@@
binary operator bop = {+,-,>>,<<};
expression e, e1, e2;
@@

e =
- (
  e1 bop e2
- )

Although, your version is probably more readable, because "bop" doesn't
really look like a binary operator.

Did you try, eg

e =
- (e1 + e2)
+ e1 + e2

?  This is not a good solution, but it could be good to think about why.

julia

> thanks,
> gargi
>
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