Re: string:sub

[Philippe Lhoste <PhiLho@...>]

On 06/03/2010 01:29, David Burgess wrote:
> It seems to me that negative values of string.sub() are inconsistent
> with not only the first parameter but also with string.find().

Perhaps that's because I am French, but I have hard time to understand 
that sentence. string.sub() returns strings, no negative values.
If you refer to negative values of parameters, I don't see how they are 
inconsistent with "the first parameter".
And why it is inconsistent with string.find().
For both functions, negatives values are for indexes are explained at 
the start of the String Manipulation chapter: "When indexing a string in 
Lua, the first character is at position 1 (not at 0, as in C). Indices 
are allowed to be negative and are interpreted as indexing backwards, 
from the end of the string. Thus, the last character is at position -1, 
and so on."

The results of the examples you show seems consistent with this definition.

> I am boldly suggesting that the second parameter with negative indices
> behave the same as the first.

It does. If they are negative, their absolute value is relative to the 
end of the string, going backward.

> Maybe I have used too many similar functions in other languages but -1
> meaning the last character seems intuitive to me.

Perhaps you can use a wrapper around this function so it behaves as you 
expect? Or your own function.
Lua, in many ways, isn't like the other languages, that's part of its 
charm... :-)

--
Philippe Lhoste
--  (near) Paris -- France
--  http://Phi.Lho.free.fr
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