This is not necessarily the current version of this TIP.This is not necessarily the current version of this TIP.
| TIP: | 351 |
| Title: | Add Striding Support to lsearch |
| Version: | $Revision: 1.1 $ |
| Authors: |
Peter da Silva <peter at taronga dot com> Donal K. Fellows <donal dot k dot fellows at manchester dot ac dot uk> |
| State: | Draft |
| Type: | Project |
| Tcl-Version: | 8.7 |
| Vote: | Pending |
| Created: | Thursday, 09 July 2009 |
This TIP allows the searching of lists that are grouped into collections of several elements.
When operating on strided lists (for example key-value lists) it's normal to convert them between lists and arrays and back again. If it was possible to efficiently perform a strided search of the list it would be possible to (for example) search just the keys and ignore the values. Indeed, Tcl has a long tradition of working with lists which are structured into groups through foreach and array get, and this is strengthened further with dictionaries TIP #111 and striding sorts TIP #326. However, there is currently no facility for searching such lists; this TIP proposes fixing this.
We propose adding a -stride option to lsearch, by exact analogy with the option added to lsort in TIP #326, whose semantics it should closely match. When lsearch is returning indices, it should return the indices of the first element of the striding group(s) that is/are being indicated.
In this example, the variable kvlist holds a key-value list (e.g., a dictionary).
set index [lsearch -stride 2 $kvlist $key] puts [lindex $kvlist $index+1]
This document has been placed in the public domain.
This is not necessarily the current version of this TIP.