OpenEuphoria

RE: match() in depth!

• Posted by bensler at mail.com Feb 24, 2002
• 501 views

> > If we use some symbolic representation of the test sequence above it 
> > could be
> > coded as :
> > 
> >  {TIAtOM} 
> > 
> > where I've simple replaced each word with a letter representing that 
> > word.
> > 
> > Thus the find for "is" similarly coded is match({I}, test). This will 
> > return 2.


{TIAtOM} = parse("this is a test of match()",32}
^ this should really be {T,I,A,T,O,M}

I = "is"
I[1] = 'i'

> > The scan for the "s" word is coded match({S},test) and returns 0 because 
> > there
> > is no "s" word in the test sequence.
> 

This is a bit confusing. match({S},test) will not return 0, it will fail 
with "variable not defined", because there is no S variable.

> You lost me there. You said match({I}, test), which i understand, but 
> that is 
> {I}, same as "I", which meets the specs for match() in the help files. I 
> used 
> {"I"}.

{I} != "I"
{I} = {"is"}
{"I"} = {{'I'}} -- (confused again? :P)


> > May I recommend trying to locate "is" word in a standard Euphoria 
> > sequence
> > string by doing :
> > 
> >    find (" is ", test) -- Note the spaces around the word. This might save 
> >    you
> >    parsing it too often.
> 
> I know that works too, same thing about the {" "}  though. But about 
> parsing 
> it too often, i parse the lines once, then each item is a slice, and i 
> deparse 
> before writing each out again. There is at least one change on each of 
> 200,000+ lines, and some have dozens of changes.

The reason I asked if find() was faster than match() is because that is 
what I thought, but you confused me with match({"is"},test) :)

find(x,s) will compare x against any ELEMENT of s
match(x,s) will compare x against any SLICE of s

EXAMPLE:
  find("the","look for the matching element")
returns 0, because there is no element that matches "the"

  find("the",parse("look for the matching element",32))
returns 3

  match("the","look for the matching slice")
returns 10


If you're parsing every line, find() should be quite a bit faster.
  find("is",parse("this is a test",32))

If you only need to find one word in the string, match() without parsing 
is faster.
  match(" is "," " & "this is a test" & " ") -- you'll need the 
concatenated spaces so you can compare the first and last slices


Chris