TIP #393: ADD -COMMAND OPTION TO LSEARCH 
==========================================
 Version:      $Revision: 1.2 $
 Author:       Pawel Salawa <pawelsalawa_at_gmail.com>
 State:        Draft
 Type:         Project
 Tcl-Version:  8.7
 Vote:         Pending
 Created:      Monday, 25 April 2011
 URL:          https://tip.tcl-lang.org393.html
 Post-History: 

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 ABSTRACT 
==========

 This document describes new option for *lsearch* named *-command* that 
 lets the developer define a custom comparision algorithm for searching 
 for an element of a list. 

 RATIONALE 
===========

 The *-command* option would be very useful when someone wants to look 
 for element on list, that contains objects (TclOO, Itcl, etc), or 
 simply Tcl dicts. Specifying a command lets a developer to decide what 
 data from objects in a list is important for the comparison. 

 This is effectively introducing the *-command* option from *lsort* to 
 *lsearch*. 

 SPECIFICATION 
===============

 The option *-command* takes additional argument, which is a name of a 
 command prefix that implements the comparison. The command prefix will 
 have two extra arguments added during evaluation, being (1) the element 
 of the list and (2) the pattern that is being sought. Thus, a suitable 
 command might be defined like: 

       proc searchCommand {listElement pattern} {...}

 And used like: 

       lsearch -command searchCommand $list $pattern

 The command must return a boolean value, where true means that the 
 element matches the pattern. Since the *-command* option specifies a 
 comparision method, therefor it's treated the same way as *-exact*, 
 *-glob*, *-regexp* and *-sorted* options are. It also causes some 
 options (e.g., *-integer*, *-nocase*) to be ignored. 

 REFERENCE IMPLEMENTATION 
==========================

 <URL:http://sqlitestudio.pl/tcl/patches/tip-393-lsearch-command.patch> 

 Patch made against 8.6.0 beta. 

 COPYRIGHT 
===========

 This document has been placed in the public domain. 

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