lrepeat was defined in TIP 136 [http://www.tcl.tk/cgi-bin/tct/tip/136.html] , 
which has been approved for incorporation into Tcl 8.5.0 .

Eventually, the doc will be here:
http://www.tcl.tk/man/tcl8.5/TclCmd/lrepeat.htm

 lrepeat number element1 ?element2 element3 ...?

This command builds up a list by repeating elements.  It will be a part of
Tcl 8.5.0 .  Note that Tcl 8.5 is available in an early developer form from ftp://ftp.tcl.tk/pub/tcl/nightly-cvs/tcl-*gz .  Early access to Tk 8.5 is there as well.

An example of how it will work is

 lrepeat 3 a => a a a
 lrepeat 3 [lrepeat 3 0] => {0 0 0} {0 0 0} {0 0 0}
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[RS]: Note the possible confusion with [string repeat]'s syntax:
 % string repeat a 5
 aaaaa

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[FW]: A forward-compatible version for versions before 8.5 is available in [Additional list functions]
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[LES] How is '''[[lrepeat 3 a]]''' different from '''[[string repeat "a " 3]]'''? 

[RS] The first creates a list, while the second creates a string thar can be parsed into a list. For short lists, this doesn't matter much, but I noticed extra time costs of about half a second when converting a 2000x2500 list-like string to a nested list.

And how is '''lrepeat 3 [[lrepeat 3 0]]''' different from '''string repeat [[list [[string repeat "0 " 3]]]] 3'''?
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[Category Command]