Subcommand of [dict] that returns a subset of a dictionary according to some filtering rule.
    :   '''dict filter''' ''dictionaryValue'' '''key''' ?''globPattern'' …?
    :   '''dict filter''' ''dictionaryValue'' '''value''' ?''globPattern'' …?
    :   '''dict filter''' ''dictionaryValue'' '''script {''' ''keyVar valueVar'' '''}''' ''script''
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[HaO]: an example session with the script option:

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% set d [dict filter {k1 v1 k2 v2} script {k v} {return [expr {$k eq "k1"}]}]
1
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So return might not be the right command. It stops the script and nothing is assigned to d.

Lets try without it:
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% set d [dict filter {k1 v1 k2 v2} script {k v} {expr {$k eq "k1"}}]
k1 v1
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That worked !

[Lars H]: Also note the following possibility
 % dict filter {k1 v1 k2 v2 k3 v3} key k1 k3
 k1 v1 k3 v3
(When there is a list of exact entries you want to keep, then the '''key''' form may be more convenient.)

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[Fabricio Rocha] - 21 Jul 2011 - Could anyone who know the [dict] internals tell about how does the search performed by '''dict filter''' works? And how it performs in comparison to searches made with '''dict for''' and other "manual", script-based search methods?

[Lars H]: Except for a few cases that can be optimised, [dict filter] works very much like the obvious script-level emulation in terms of [dict for]. For example, they both use the same public Tcl_DictObjFirst/Tcl_DictObjNext interface for iterating over the dictionary elements. A [dict filter] is however likely to be faster whenever that is precisely what you wants to do, due to less overhead for updating Tcl variables and such.
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!!!!!!
%| [Category Command] |%
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