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- Subject: Re: New function table.edge (was Re: Lua 5.2 Length Operator and tables (bug?))
- From: Dirk Laurie <dirk.laurie@...>
- Date: Fri, 27 Apr 2012 16:11:31 +0200
There has been no discussion of the proposal below, which means that
it is either above or below criticism.
> * table.edge(tbl[,k])
> Returns the first at most k edges in tbl, where an edge is a
> non-negative integer n such that tbl[n] is not nil but tbl[n+1] is
> nil, except that 0 is an edge when tbl is nil no matter what tbl
> is. edge(tbl,-k) returns the last at most k edges. In particular,
> edge(tbl,-1) returns the largest positive integer index in the table,
> or 0 if the table is empty.
> edge(tbl,0) returns one arbitrarily chosen edge. Which edge this
> will be is undefined except when there is only one edge, i.e. the
> table is empty or a proper sequence, in which case edge(tbl) returns
> the number of elements in the sequence.
> The default value of k is 0.
> table.edge(t,1) --> 0
> table.edge(t,100) --> 0,3,8,10,30
> table.edge(t,-1) --> 30
> table.edge(t,0) --> 10 -- for Lua 5.2 on my laptop
> During the discussion of the length operator, one could simply say that
> by default, #tbl returns table.edge(tbl), and that only in the case of
> sequences does this correspond to the intuitive notion of length.