Re: [TCLCORE] TIP #351: Add Striding Support to lsearch

[Kieran E. <kie...@or...>]

Peter da Silva wrote:
> 
> lsearch -index 0 -stride 2 would search the first subelement of every  
> second element. The default behavior of lsearch -stride would be "- 
> index {}".
> 

What if one wants to search every (2n+1)th element?

e.g. all the values in a {name value name value ...} list.

There doesn't seem to be any way to achieve this with the
proposal as it stands - despite being an important use case.

It's also rather inconsistent with the -stride option I
proposed for lsort; from TIP #326:

   If -stride is supplied, the list will be treated as
   consisting of groups of grpSize elements, and the groups
   will be sorted by either their first element or, if the
   -index option is used, by the element within each group
   given by the first index passed to -index (which is then
   ignored by -index).

So to sort by the first subelement of every second element,
one would do:

   lsort -stride 2 -index {0 0}

To sort by the values in a {name value name value ...} list,
one would do:

   lsort -stride 2 -index 1

If -index is not used, then lsort with -stride operates on
the first element in each group; I guess this could be
thought of as changing the default of -index to be 0 when
-stride is used, though I didn't word it like that.

Regards,
Kieran Elby