Re: [Help-source-highlight] Regular Expression Explanation for 'function.lang'

[Lorenzo Bettini]

On 05/20/2011 04:57 PM, Peter Willis wrote:
> Hello,

Hi Peter

> I have made an IDL syntax highlight file:
> rsiidl.lang
>
> One of the included files is 'function.lang'.
> This works fine for functions that return a value
> since the call syntax for functions is:
>
> VARIABLE = SOMEFUNC(variable , variable, ...)
>
> I now want to define 'procedure.lang' where
> the call syntax is:
>
> SOMEPROC, variable, variable, ...
>
> As you can see the call to a procedure in IDL does
> not include parenthesis.

please keep in mind that source-highlight does not perform real parsing 
(only scanning with some state functionalities), thus it can only 
highlight parts of a program that can be recognized through regular 
expressions...

> 'function.lang' reads as follows:
>
>
> vardef FUNCTION = '(?:[[:alpha:]]|_)[[:word:]]*[[:blank:]]*(?=\()'
> function = $FUNCTION
>
> What format (of regex ??) is being used here?
> How might I change this to test just the 'procedure' case?

that regular expression uses "Forward Lookahead Asserts" (see also 
http://www.gnu.org/software/src-highlite/source-highlight.html#Notes-on-regular-expressions), 
i.e., which are included in (?=   )

(?=\()

checks whether after the name there's a ( but does not consume it

can the syntax of your procedure definition be identified with a regular 
expression?

Can you make some examples of procedures?

cheers
        Lorenzo

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Lorenzo Bettini, PhD in Computer Science, DI, Univ. Torino
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