OpenEuphoria

Re: Reading a file into a "sequence"

• Posted by Derek Parnell <ddparnell at bigpond.com> Nov 18, 2004
• 557 views

Derek Parnell wrote:
> 
> John F Dutcher wrote:
> > 
> > You guys do a heck of a job...
> > The sub routine is a nice piece of work....
> > This is returned in "ex.err"  when called with the input below &
> > the code lines below:
> > 
> >     "sequence lengths are not the same (4 != 0)"

Actually, the error message you get is really about a problem when
creating that temporary sequence I talked about earlier. 

The problem is caused by the '=' symbol having three distinct semantic
roles in Euphoria. 
(1) ASSIGNMENT: To copy the value of the thing to the right of it to
   the thing on the left of it.
(2) EQUALITY TEST: To see if the thing on the left has the same value 
   as the thing on the right.
(3) SEQUENCE OPERATION EQUALITY FUNCTION: Return a sequence such that each
   element reflects the result of an equality test on the respective
   elements in the right hand and left hand sequences.

Which operation is actually performed depends on the context that the
'=' symbol is found in by the interpreter. RDS has decided that role (3)
is the appropriate one to use in the context of an IF statement when one
of the expressions in the conditional expression is a sequence. Most of 
the rest of us would expect role(2) to be performed, but oh well, we can't
all be right, can we. 

Anyhow, when Euphoria sees your "Fields = {}" it tries to perform role(3).
But, in order to do that operation, the sequences on either side of the
'=' symbol must be the same length. In your case, you have 'Fields' 
which contains four elements (fields) and '{}' which contains zero
elements. Thus the error message.

If however, 'Fields' had have been an empty sequence, Euphoria would have
created a temporary (empty) sequence and then you would have got the 
error message "true/false condition must be an ATOM". 

-- 
Derek Parnell
Melbourne, Australia