Re: do you use the pre-processor?

[Roberto Ierusalimschy <roberto@...>]

On Fri, 12 May 2000, Dave Gordon wrote:

> | 
> | How about starting it with "comment = [[" and ending with "]]".  That's
> | what I usually do...
> 
> That's a good idea, but it doesn't work well in some cases.  At least 
> I don't see a way to make it work in a situation I encounter often 
> while debugging my renderer.  I use $if, $end to comment out sections 
> of large data arrays (vertex and polygon lists to be precise) to try 
> to locate regions of the data were a problem is occuring.  For that
> purpose "comment = [[...]]" doesn't work because (I believe) there's 
> no valid syntax that allows it to be put it in the middle of table
> constructor consisting of a list of objects.  So unless there's 
> another trick I'm missing I still think a block comment delimiter 
> would be helpful.  That is in the absence of $if, $end of course.

There is a valid syntax for this case (a dirty trick, in fact)! If you
have a constructor like

  a = { 1.0, 2.0, 3.0, 4.0, 5.0 }

you can remove part of it with 

  a = { 1.0, [[2.0, 3.0, 4.0,]] and 5.0 }

A string is always true, so this `and' results in its second operand. It
does not work only when you want ro remove a sufix of the constructor.

-- Roberto