Generic IO interface (was: whatever happened to io.popen() ?)

[Rob Kendrick <lua-l@...>]

Roberto Ierusalimschy wrote:

> > Or actually, a step better than that - abstract the whole lot so it's
> > easy for people to create IO methods that use the same interface?
>
>
> That would be nice. Suggestions?

I'm no software engineer, but what about something along the lines of the 
handle returned by io.open() or user-provided functions for other types of 
file be a table, with a "handle" field that can be anything the supporting 
library wants to put in it (a userdata with a FILE* or fd in it, or a table 
with two handles in it, for bidirectional pipes, and such), and then functions 
with names similar to the io. interface (read, write, close, and such) that 
the io. functions call to do the work.

I'm sure there are more elegant ways of doing it, but this way would certainly 
be simple to use.

Something I've always pined to be able to do is handle[n] to get the nth byte, 
or similar, which could then be easily added yourself if you wanted.

On an semi-unrelated note, is there a nice way, or 'standard' interface for 
getting slices out of types?  (ie, t[4..6] on a table returns a new table with 
entries 4 to 6 from t, or s[10..90] to get that range from a string?)

--
Rob Kendrick, Pepperfish Ltd.         +44 (0)845 226 4146  www.pepperfish.net
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