OpenEuphoria

Re: true/false atoms?

• Posted by Kat <KSMiTH at PELL.NET> Aug 12, 1999
• 528 views

----- Original Message -----
From: Pete Eberlein <xseal at HARBORSIDE.COM>
To: <EUPHORIA at LISTSERV.MUOHIO.EDU>
Sent: Thursday, August 12, 1999 1:50 AM
Subject: Re: true/false atoms?


> > >while  datafound = "false"  or  data != -1  do
> >
> > The '=' operator can't be used here. Try instead:
> >
> >     while equal( datafound, "false" ) or data != -1 do
>
> While this solves the first "Error: true/false condition must be an atom",
> the second test "data != -1" will cause the same error.  You must declare
> data as an "object" because the gets function will return -1 when it
> reaches end-of-file.  "But that's I'm testing for!!!" you say, but
> remember all the while data will be a sequence of text read from the
> file... for instance say data holds {1,1,2,3,5,8}.  The result of "data !=
> -1" will be "{1,1,2,3,5,8} != -1" whose result is the same as "{1 != -1, 1
> != -1, 2 != -1, 3 != -1, 5 != -1, 8 != -1}" or "{1,1,1,1,1,1}".  When an
> sequence is applied to an atom using an arithmetic operator, the atom is
> applied to each element of the sequence.  So the result is still a
> sequence and the "true/false condition must be an atom" error will be
> reported.
>
> The solution: declare data as an object and use the sequence() function to
> test data to make sure it is a sequence.
>
>   while equal( datafound, "false" ) or sequence( data ) do
>
> Since the only time gets() returns an atom is when it returns -1, it is
> safe to use the sequence() test to check for end-of-file.

The newer code, with David's and Pete's code:

while equal( datafound, "false" ) or sequence( data ) do
       data = gets(dctstrfile)
       if ( find(datatofind,data) != 0 )
        then datafound = "true"
       end if
    end while

It still faults at the find() when data is set to -1 ( which i must say,
happens extremely fast compared to the pascal compiled code! ) , so i must
set yet another if test....

while equal( datafound, "false" ) or sequence( data ) do
       data = gets(dctstrfile)
       if sequence(data) and ( find(datatofind,data) != 0 )
        then datafound = "true"
       end if
    end while

Now it misses the end of file, and keeps on running, doing nothing..... no
errors, nothing, it never leaves the while loop. I put a printf, gets , and
abort after the while, to see if it was leaving the while loop,, and the
printf never is hit,, so i told it to print out the file in the while loop,
it got to the end of the file and printed blank lines. I had opened the file
as "rb" (i have non-char tokens in it) , and changed it to "r", to no
effect.

Any ideas? Please?

Kat