Re: file:read("*n") reference manual entry improvement

[behoffski <behoffski@...>]

In October 2013, Egil, Roberto wrote:
> > Anyway, it seems we both agree the C documentation is quite convoluted
> > about this topic.  So, the question remains whether it is worth trying
> > to explain something similar in the Lua manual, versus leaving it open
> > to the user's imagination or own tests...
> >
> > -- Roberto
> I would suggest a note that file:read("*n") (being based on based on C function fscanf)
> is  not recommended unless it is certain that the stream return a valid textual number.
> Egil

There are several levels of parsers available to the user:
    - The ANSI C's strtod() function as provided via the scanf() family of functions;
    - Lua's string library, with its pattern-matching facilities;
    - Writing a parser more explicitly in Lua, with the possibility of extending
      and/or replacing the hand-crafted the Lua code with C code as desired;
             ...and a more recent addition:
    - Using more explicit lexical analysers/compiler libraries such as LPeg.

The introduction of LPeg has changed the nature of the terrain somewhat; my
suspicion is that a future version of PiL might contain at least a pointer to
LPeg when discussing parsing text.

Laying out a list of options, ranging from simple to complex, as given above,
may give the reader a "heads-up" about the potential complexity of the
problem, and show some of the existing solutions, with varying power/complexity
engineering trade-offs, that are available to tackle the task.

cheers,

behoffski