Re: [PATCH v5] userdiff: add builtin diff driver for kotlin language.

[jaydeepjd.8914@gmail.com]

Sorry for the late reply. 

On 3/9/22 12:02 AM, Johannes Sixt <j6t@kdbg.org> wrote:
> Am 08.03.22 um 17:54 schrieb jaydeepjd.8914@gmail.com:
> > So, the final regexes are these, right?:
> 
> Not quite.
> 
> >
> >       "[a-zA-Z_][a-zA-Z0-9_]*"
> >       /* hexadecimal and binary numbers */
> >       "|0[xXbB][0-9a-fA-F_]+[lLuU]*"
> >       /* integers and floats */
> >       "|[0-9][.]?[0-9_]+([Ee][-+]?[0-9]+)?[fFlLuU]*"
> 
> This would not match 12.5 because you allow only a single digit before
> the decimal point. Perhaps
> 
> 	"|[0-9][.0-9_]*([Ee][-+]?[0-9]+)?[fFlLuU]*"

Okay. 

> >       /* floating point numbers beginning with decimal point */
> >       "|[.][0-9][0-9_]*([Ee][-+]?[0-9]+)?[fFlL]?"
> >       /* unary and binary operators */
> >      
> > "|[-+*/<>%&^|=!]?==?|--|\\+\\+|<<=|>>=|&&|[||]|->|\\.\\*|!!|::|[?:.][.:]"),
> 
> [||] does not work as you intend. A new suggestion: do not start with an
> initial optional character in order to reduce the number of
> backtrackings that the regular expression evaluation has to do. I would
> write this line as
> 
> 	"|[-+*/<>%&^|=!]==?|--|\\+\\+|<<=|>>=|&&|\\|\\||->|\\.\\*|!!|::|[?:.][.:]"),
> 
> BTW which operators are handled by "[?:.][.:]"? I'm asking because you
> list :: separatly that would also be matched by this sub-expression.

It matches the following operators: `?:`, `?.`, `..` `::`. Although matching `::` is
unnecessary since its matched before.

https://kotlinlang.org/docs/keyword-reference.html#operators-and-special-symbols