Re: request for isprint character class code in string.gsub patterns

[Rici Lake <lua@...>]

Have you looked at the %q string.format code ?

On 24-Sep-04, at 3:55 PM, David Jones wrote:

> I'm writing a function to quote a string, that is, it takes a string 
> and returns a string that when printed is acceptable as a lua literal 
> (and the literal is equal to the passed string).
>
> Has anyone already written such a code?  (And is it freely available)  
> It seems like such a commonly needed function.
>
> There's a bit in this function where it expands unprintable codes to 
> the \nnn representation.  It currently looks a bit like this:
>
> string.gsub("\7ab","[^ %p%w]", function(x)return 
> '\\'..string.byte(x)end)
>
> What I want to do is match all non-printable characters.  C provides 
> this concept via isprint and isgraph, but in Lua I have to use the 
> union of " ", "%p" (punctuation), and "%w" (alphanumerics).  Which 
> relies on isprint being a union of space, isprint, and isalnum (which 
> the C standard guarantees, but it seems tenuous).
>
> Would it be possible to have another % code for the isprint character 
> class? %t perhaps (for typeable or text)?  From a completeness aspect 
> I suppose we should also have one for isgraph.  Or do The Implementors 
> think that the current situation, synthesis via %w and %p, is ok?
>
> David Jones