Re: allowing value evaluations as statements

[Rici Lake <lua@...>]

On 31-Dec-06, at 9:56 PM, askok@dnainternet.net wrote:

> A perl-ish way of making error checking, but neat and effective:
>
> _= nsfm:fileExistsAtPath(testfile)
>     or error "File doesn't exist!"
>
> _= nsfm:copyPath( testfile, newfile )
>     or error "File copy failed!"
>
> Currently, Lua does not allow leaving the "_=" away, since that would 
> make these commands and commands don't have a value ('or' gives this a 
> value).
>
> In my opinion, evaluation results could be allowed even if the value 
> is not stored anyway.  In a way, they would have a "drain" that eats 
> up the value.
>
> I do know that by a function this can be overcome, but the neaty is to 
> have the essential thing first (the command), and ability to switch 
> on/off the error check by simply commenting that out.  Anyways, this 
> is caused by my exposure to perl lately, it does show. Perl has a lot 
> of those thisandthat or die things..  Which I actually like(d).

But what's wrong with:

assert(nsfm:fileExistsAtPath(testfile), "File doesn't exist!")

Or even, if fileExistsAtPath follows normal Lua conventions of
returning <nil/false, error message>,

assert(nsfm:fileExistsAtPath(testfile))

?

Another (perhaps warped) possibility is:

repeat until nsfm:fileExistsAtPath(testfile)
   or Shriek "File doesn't exist"