OpenEuphoria

RE: Replacing characters (Matt: bug)

• Posted by Andy Serpa <renegade at earthling.net> Sep 17, 2002
• 454 views

Derek,

Yours fails if "a" is longer than "b"...

-- Andy


Derek Parnell wrote:
> Hi Matt,
> unfortunately the algorithm doesn't work.  Try this test ...
> 
>   x = replace_all2("derekderekderekderek", "rek", "1234567")
> 
> this returns "de1234567derek1234567ekde1234567"
> 
> rather than "de1234567de1234567de1234567de1234567"
> 
> 
> Anyhow, here is another method of doing it...
> 
> function replace_elem(sequence s, object a, object b)
>     sequence t
>     integer n,m
> 
>     if atom(a) then
>         a = {a}
>     end if
> 
>     if atom(b) then
>         b = {b}
>     end if
> 
>     -- Create a buffer big enough to cater for worst case replacement.
>     t = repeat(0, (floor(length(s) / length(a)) + 1) * length(b))
> 
>     m = 1
>     while 1 do
>         n = match(a, s)
>         if n then
>             t[m..m+n-2] = s[1..n-1]
>             m += (n-1)
>             t[m..m+length(b)-1] = b
>             m += (length(b))
>             s = s[n+length(a) .. length(s)]
>         else
>             t[m..m+length(s)-1] = s
>             m += (length(s))
>             exit
>         end if
>     end while
> 
>     return t[1..m-1]
> end function
> 
> 
> ----------------
> cheers,
> Derek Parnell
> ----- Original Message -----
> From: "Matthew Lewis" <matthewwalkerlewis at YAHOO.COM>
> To: "EUforum" <EUforum at topica.com>
> Sent: Tuesday, September 17, 2002 9:23 PM
> Subject: RE: Replacing characters (Matt: bug)
> 
> 
> > > From: Dan Moyer [mailto:DANIELMOYER at prodigy.net]
> >
> > > Matt's now doesn't fail on replace last character, but
> > > doesn't actually
> > > replace the last character, & is *very* much slower than
> > > either of the other
> > > two
> > >  (one test: Henri: 3.9, Andy:  2.75 , Matt:  24.06) ;
> >
> > It seems to replace the last char when I test it.  I believe that the
> > slowness is due to the use of subscripting within the call to match().
> > There was some discussion about this recently.  I typically run fairly
> short
> > strings through this routine (maybe 2 or 3 sentence lengths) at a time, 
> > so
> > I've never needed any more speed.
> >
> > > Henri/Mike "vulcan" routine is faster than Matt's but won't
> > > replace one char
> > > with 2;
> > >
> > > Andy's is fastest. How much faster seems to vary.  On a
> > > "long" sequence to
> > > peruse, it seemed twice as fast as Henri/Mike "vulcan", but on many
> > > repetitions of replacing in smaller sequence, it seems only
> > > 1.4 times faster
> > > (see test results above).
> >
> > Actually, neither one will handle replacements of different lengths.  
> > This
> > was a definite requirement for what I needed, where, for instance you
> might
> > want to replace "." with "..".  Also, neither routine will handle:
> >
> > R/replace_in_string("abc cba", "ab", "12" )
> >
> > Both return "12c c21", which is fine if you've got a cipher (did anyone
> use
> > this method in the contest? :), but not if you're trying to replace 
> > words
> > with other words, in which case you end up with garbage.  Henri talks
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