OpenEuphoria

RE: Sequence Slicing (Was RE: Tough ciphers?)

• Posted by bensler at mail.com Mar 15, 2002
• 418 views

This is fast and works on any slice of a sequence. Sanity checks could 
be added.

function range_find(object x, sequence s, integer pos1, integer pos2)
 atom found
   found = 0
   while not found and pos1 <= pos2 do
      found = equal(x,s[pos1]) * pos1
      pos1 +=1
   end while
   return found
end function

This is the test that I used. I wasn't concerned with accuracy, because 
the routine beats find() by a long shot.

<TEST>
include file.e

integer fn,fl
fn = open("words.txt","rb")
fl = seek(fn,-1)
fl = where(fn)
if seek(fn,0) then end if

sequence temp     temp = repeat(0,fl)

for i = 1 to fl do
   temp[i] = getc(fn)
end for

close(fn)

function range_find(object x, sequence s, integer pos1, integer pos2)
 atom found
   found = 0
   while not found and pos1 <= pos2 do
      found = equal(x,s[pos1]) * pos1
      pos1 +=1
   end while
   return found
end function

atom t   t=time()
integer count  count = 0
integer f,found
f=0
found=find('\n',temp)
while found != 0 do
   count +=1
   f = found+1
   found = range_find('\n',temp,f,length(temp))
end while
? f
? count
? time()-t
while get_key()=-1 do end while
<END TEST>

The control test used:
found = find('\n',temp[f..length(temp)]

instead of:
found = range_find('\n',temp,f,length(temp))


I didn't try with shorter sequences.

Chris

C. K. Lester wrote:
> bensler at mail.com wrote:
> > The problem that Derek is pointing out, is that you still
> > have to slice your sequence to do consecutive finds.
> 
> I guess what he's suggesting is "give us an optimized find on a slice," 
> right?
> 
> Rob, why not?! :)
> 
>