Re: if statement not working
On 22 Mar 2002, at 9:47, kbochert at ix.netcom.com wrote:
>
> Hi David Cuny, you wrote on 3/22/02 7:04:39 AM:
>
> >To reiterate:
> >
> >0. The goal is to write safe string handling code.
> >1. Slices (by themselves) are unsafe when working with strings.
Before someone nails down "type string", lets make all sequence handling
safe, regardless of what's stored in it.
> >2. Guarded slices are unsafe because the guard isn't coupled to the string.
> >3.
> >Euphoria doesn't provide any built-in routines for creating substrings.
Unless you parse() the string (err, sequence) and such. Really, i mix what i
think most people call "string" with nested sequences. I'd hate to see
restrictions put on what can or cannot be a "string", Eu's strength is the
sequence. For instance, if you nail down a string to be atoms of 1-255, you
can't handle most of the world's language characters gracefully (old thread
from yrs ago). This would hurt translation dictionaries for one, and could
artificially restrict the countries that use Eu, as well as the knowledge
domains that use it (like all those calculus and trig symbols).
> How about a new operator '=~'
First thought: ~ like "fuzzy logic"? Hmmm, better write that as a real optional
include at this point, Rob will never sign onto it.
> that acts like '=' except that it
> plows on ahead in the face of errors:
> s =~ t[2..4]
> -- s is padded to length 3 if necessary
Since you specified [2..3], why pad s some more? And with what? Better to
look at what t actually has, and deliver what is in the envelope of [2..3] and
no more. If [2..3] doesn't exist, then return {}. If you asked to borrow a book
that i don't have, i won't pad out a empty box of non-existant book with some
random selection of book parts.
> if s[2..4] =~ '123' then
> -- comparison fails if s is too short
> -- (or uninitialized!)
In this case, if s is too short, it's not equal. You did a test there, not an
extraction or assignment, it obviously fails, but shouldn't bomb the whole
program. In mirc, if i do:
if ( $gettok(%address,2,$asc(.)) == ipt ) { whatever }
and %address has nothing in it this time, because of whatever, i expect this
boolean test to fail, not the entire program. In Eu, i expect the whole program
to crash horribly.
> I suppose the postfix '~' could also be applied elsewhere:
> s = t[2..8]~ --s has 6 elements even if t has 4
> But I haven't thought too much about that.
Nononononono! In this case, if t has 6 elements, Eu should grab the [2..6] of
them for s, making s have 5 elements.
Basically, if Eu would crash on it because of a length, either preemptively
handle it, or grab the error Eu throws now, and deal with it intelligently.
Don't
add anything to it, because whatever you add might be tested for later on
and cause an error.
Kat
|
Not Categorized, Please Help
|
|
