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From: cargo@TARDIS.CRAY.COM (David S. Cargo)
Newsgroups: comp.lang.icon
Subject: deleting characters
Message-ID: <9001192303.AA01299@zk.cray.com>
Date: 19 Jan 90 23:03:16 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Distribution: inet
Organization: The Internet
Lines: 81

After sending out my mail about deleting or stripping characters out of a
string I received a couple of responses from kindly Iconists.  I later was
showing off Icon to a friend when I notices a "delete" function in
strutil.icn.  Upon closer examination I found that delete also did what I
wanted.  The next step for me was to write a little benchmarking program so
I could see how the different methods compared speedwise.  It turns out
that the IPL delete routine was the slowest, although the fastest was only
15 percent faster.

Here is the test program:

procedure main()
    test_string :=
        "    str ? while tab(upto(chars)) do text ||:= tab(many(chars))"
    remove := &cset -- &lcase
    time1 := &time
    limit := 1000
    every 1 to limit do result1 := delete(test_string, remove)
    time2 := &time
    every 1 to limit do result2 := strip1(test_string, remove)
    time3 := &time
    every 1 to limit do result3 := strip2(test_string, remove)
    time4 := &time
    write(time1)
    write(time2-time1, " ", result1)
    write(time3-time2, " ", result2)
    write(time4-time3, " ", result3)
    return
end

#  from IPL strutil.icn
#  delete characters
#
procedure delete(s,c)
    local i
    while i := upto(c,s) do
        s[i:many(c,s,i)] := ""
    return s
end

#From: Richard Goerwitz <goer@sophist.uchicago.edu>
procedure strip1(s,c)
    s2 := ""
    s ? {
        while s2 ||:= tab(upto(c)) do
            tab(many(c))
        s2 ||:= tab(0)
        }
  return s2
end


#From: Chris Tenaglia - 257-8765 <tenaglia@mis.mcw.edu>
procedure strip2(str,chrs)
    local text,chars
#    /chrs := ' '
#   (I commmented this out because the others don't do such checks.)
    chars := &cset -- chrs
    text  := ""
    str ? while tab(upto(chars)) do text ||:= tab(many(chars))
    return text
end

And the output (first column is time, second column is the result string
which is always supposed to be the same).  Initial time is 0, other times
are in milliseconds.

0
21033 strwhiletabuptocharsdotexttabmanychars
20350 strwhiletabuptocharsdotexttabmanychars
17717 strwhiletabuptocharsdotexttabmanychars

All three are reasonable, but the differences in approach are educational.
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