lua-users home
lua-l archive

[Date Prev][Date Next][Thread Prev][Thread Next] [Date Index] [Thread Index]

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
--  --  --  --  --  --  --  --  --  --  --  --  --  --