Re: How to turn a very long list into smaller lists
- From: Jonathan Bromley <jonathan.bromley@xxxxxxxxxxxxx>
- Date: Fri, 30 May 2008 15:56:24 +0100
On Fri, 30 May 2008 07:30:40 -0700 (PDT), Mel wrote:
I have a list that is very long and I need to break it into smaller
lists of say 50 elements (the original list is a muliple of 50.
as for now I am just using lrange function which is extremy slow on a
long list of say 100000 items.
On my not-very-fast Windows PC, this proc breaks up a
list of 1,000,000 elements into a list of 20,000 fifty-element
lists, in about an eighth of a second. Is that too slow for
you? I was quite impressed...
proc split_list {L {n 50}} {
incr n 0; # thanks to RS for this cool "is it an int" check!
set result {}
set limit [expr {[llength $L] - $n}]
for {set p 0} {$p <= $limit} {incr p $n} {
lappend result [lrange $L $p [expr {$p+$n-1}]]
}
return $result
}
What are you doing that is "extremely slow" ? I suspect
you are doing something that causes the list to be
shimmered back and forth between list and string
representation internally.
--
Jonathan Bromley, Consultant
DOULOS - Developing Design Know-how
VHDL * Verilog * SystemC * e * Perl * Tcl/Tk * Project Services
Doulos Ltd., 22 Market Place, Ringwood, BH24 1AW, UK
jonathan.bromley@xxxxxxxxxxxxx
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