1. match()
match("", "something") shows an error
first argument of match() must be a non-empty sequence
I think it should return 1, because "" is a substring of "something",
and is located in any position.
So I don't have to check if the first argument is "", don't call
match().
How do you think?
2. Re: match()
On Mon, 26 May 2003 13:30:41 +0700, aku saya <akusaya at gmx.net> wrote:
>
>
> match("", "something") shows an error
> first argument of match() must be a non-empty sequence
>
> I think it should return 1, because "" is a substring of "something",
> and is located in any position.
>
> So I don't have to check if the first argument is "", don't call
> match().
>
> How do you think?
One way of looking at this is to ask "Where does NOTHING first appear in
the string?". And there is no meaningful answer to that.
To be consistent, I would have preferred that match() return zero,because
the empty string wasn't found in the target string. But because that too is
debatable, just disallowing it might be the best (unambiguous) way to
handle it.
And if we look at it the way you suggested, "because "" ... is located in
any position" then any random number between 0 and the length of the target
string would be just as valid.
--
cheers,
Derek Parnell
3. Re: match()
Hello Aku, you wrote:
> match("", "something") shows an error
> first argument of match() must be a non-empty sequence
>
> I think it should return 1,
The equivalent function to match() in BASIC is instr(), and that's
actually the way instr() works.
My experience after about 10 years programming in BASIC is, that this
often causes problems. Especially it can cause bugs, that are very hard
to find by beginners.
> because "" is a substring of "something",
> and is located in any position.
This is a philosophical question, isn't it? 
> So I don't have to check if the first argument is "", don't call
> match().
>
> How do you think?
Best regards,
Juergen
--
/"\ ASCII ribbon campain | "Everything should be made as simple
\ / against HTML in | as possible, but not simpler."
X e-mail and news, |
/ \ and unneeded MIME | http://www.sfheart.com/einstein.html
4. Re: match()
- Posted by irvm at ellijay.com
May 26, 2003
On Monday 26 May 2003 03:07 am, you wrote:
>
> On Mon, 26 May 2003 13:30:41 +0700, aku saya <akusaya at gmx.net> wrote:
> > match("", "something") shows an error
> > first argument of match() must be a non-empty sequence
> >
> > I think it should return 1, because "" is a substring of "something",
> > and is located in any position.
No. If it is a valid string, *something*, i.e., an ascii character,
appears in every single position of that string. "Nothing" does not,
and can never, appear in any string.
In the string "ABC", if match("",string) were to return 1, then it's wrong,
isn't it? Because anyone can clearly see that 'A' is the first character.
And 'A' is not nothing.
Irv
5. Re: match()
Hello Irv, you wrote:
> On Monday 26 May 2003 03:07 am, you wrote:
>>
>> On Mon, 26 May 2003 13:30:41 +0700, aku saya <akusaya at gmx.net> wrote:
>>> match("", "something") shows an error
>>> first argument of match() must be a non-empty sequence
>>>
>>> I think it should return 1, because "" is a substring of "something",
>>> and is located in any position.
>
> No. If it is a valid string, *something*, i.e., an ascii character,
> appears in every single position of that string. "Nothing" does not,
> and can never, appear in any string.
>
> In the string "ABC", if match("",string) were to return 1, then it's wrong,
> isn't it? Because anyone can clearly see that 'A' is the first character.
> And 'A' is not nothing.
This is convincing. I agree, and take back my previous opinion, that
it's a philosophical question.
An empty *set* is a valid subset of any other set, but strings are
different from sets.
Best regards,
Juergen
--
/"\ ASCII ribbon campain | |\ _,,,---,,_
\ / against HTML in | /,`.-'`' -. ;-;;,_
X e-mail and news, | |,4- ) )-,_..;\ ( `'-'
/ \ and unneeded MIME | '---''(_/--' `-'\_)
6. Re: match()
Why not just return -1 then? Seems silly this should be a run-time error...
jbrown
On Mon, May 26, 2003 at 10:07:06AM +0200, Juergen Luethje wrote:
>
>
> Hello Aku, you wrote:
>
> > match("", "something") shows an error
> > first argument of match() must be a non-empty sequence
> >
> > I think it should return 1,
>
> The equivalent function to match() in BASIC is instr(), and that's
> actually the way instr() works.
> My experience after about 10 years programming in BASIC is, that this
> often causes problems. Especially it can cause bugs, that are very hard
> to find by beginners.
>
> > because "" is a substring of "something",
> > and is located in any position.
>
> This is a philosophical question, isn't it?
>
> > So I don't have to check if the first argument is "", don't call
> > match().
> >
> > How do you think?
>
> Best regards,
> Juergen
>
> --
> /"\ ASCII ribbon campain | "Everything should be made as simple
> \ / against HTML in | as possible, but not simpler."
> X e-mail and news, |
> / \ and unneeded MIME | http://www.sfheart.com/einstein.html
>
>
>
> TOPICA - Start your own email discussion group. FREE!
>
--
/"\ ASCII ribbon | http://www.geocities.com/jbrown1050/
\ / campain against | Linux User:190064
X HTML in e-mail and | Linux Machine:84163
/*\ news, and unneeded MIME |
7. Re: match()
- Posted by gertie at visionsix.com
May 26, 2003
On 26 May 2003, at 17:07, Derek Parnell wrote:
>
>
> On Mon, 26 May 2003 13:30:41 +0700, aku saya <akusaya at gmx.net> wrote:
>
> >
> > match("", "something") shows an error
> > first argument of match() must be a non-empty sequence
> >
> > I think it should return 1, because "" is a substring of "something",
> > and is located in any position.
> >
> > So I don't have to check if the first argument is "", don't call
> > match().
> >
> > How do you think?
>
> One way of looking at this is to ask "Where does NOTHING first appear in
> the string?". And there is no meaningful answer to that.
>
> To be consistent, I would have preferred that match() return zero,because
> the empty string wasn't found in the target string. But because that too is
> debatable, just disallowing it might be the best (unambiguous) way to handle
> it.
>
> And if we look at it the way you suggested, "because "" ... is located in
> any position" then any random number between 0 and the length of the target
> string would be just as valid.
I prefer it return zero also, simply because match("u","kat") also returns
zero.
Kat
8. Re: match()
Hello Jim, you wrote:
> Why not just return -1 then? Seems silly this should be a run-time error...
Yes, maybe. Although for practical purposes, I don't think there will be
a big difference. Now we write:
if length(s) != 0 then
m = match(s, main)
...
end if
Otherwise, we will write:
m = match(s, main)
if m != -1 then
...
end if
Best regards,
Juergen
--
/"\ ASCII ribbon campain | |\ _,,,---,,_
\ / against HTML in | /,`.-'`' -. ;-;;,_
X e-mail and news, | |,4- ) )-,_..;\ ( `'-'
/ \ and unneeded MIME | '---''(_/--' `-'\_)
9. Re: match()
Since match() is meant to look into a sequence for another sequence, it
looks for "something" in "something", as Juergen said.
So calling match(.,.) with one or both arguments empty is an invalid
condition. Returning -1 (just like routine_id on an unknown routine
name) seems much more flexible and adequate than throwing out an error,
so I'd push for this change.
CChris
10. Re: match()
Hi Al, you wrote:
<snip>
> On the other hand, returning
> a zero when one or both args are null wouldnt break any code.
>
> This means
>
> match("",s)
> match(s,"")
> match("","")
>
> all should return zero, without regard for what is (or isnt)
> contained within the sequence s.
<snip>
match("","") IMHO should raise an error, or return -1 (or another flag
to indicate an illegal operation), or return 1 (*not 0*).
Since match("ab","ab") returns 1, because both strings are identical,
match() for any other two strings x and y, where equal(x,y) = 1,
should never return 0. IMHO.
Best regards,
Juergen
--
/"\ ASCII ribbon campain | |\ _,,,---,,_
\ / against HTML in | /,`.-'`' -. ;-;;,_
X e-mail and news, | |,4- ) )-,_..;\ ( `'-'
/ \ and unneeded MIME | '---''(_/--' `-'\_)
11. Re: match()
Hi Al, you wrote:
> Juergen Luethje wrote:
>>
>>
>> Hi Al, you wrote:
>>
>> <snip>
>>
>>> On the other hand, returning
>>> a zero when one or both args are null wouldnt break any code.
>>>
>>> This means
>>>
>>> match("",s)
>>> match(s,"")
>>> match("","")
>>>
>>> all should return zero, without regard for what is (or isnt)
>>> contained within the sequence s.
>>
>> <snip>
>>
>> match("","") IMHO should raise an error, or return -1 (or another flag
>> to indicate an illegal operation), or return 1 (*not 0*).
>>
>> Since match("ab","ab") returns 1, because both strings are identical,
>> match() for any other two strings x and y, where equal(x,y) = 1,
>> should never return 0. IMHO.
>>
>> Best regards,
>> Juergen
>>
>> --
>> /"\ ASCII ribbon campain | |\ _,,,---,,_
>> \ / against HTML in | /,`.-'`' -. ;-;;,_
>> X e-mail and news, | |,4- ) )-,_..;\ ( `'-'
>> / \ and unneeded MIME | '---''(_/--' `-'\_)
>>
>
> hi Juergen, i like your little pic there 
<-- begin lover of cats mode -->
Thanks.
There is also a little cat running on my desktop all the time.
In case you are (or someone else is) interested:
http://luethje.de.vu/temp/felix.zip (Freeware for 32-bit Windows, 212 KB)
<-- end lover of cats mode -->
> So far i think i've agreed with you on most issues, but
> returning 1 from match with two null sequences isnt one
> of them that i can agree on.
There may be a misunderstanding, that's not what I actually was trying
to say. I wrote:
| match("","") IMHO should raise an error, or return -1 (or another flag
| to indicate an illegal operation), or return 1 (*not 0*).
Maybe I should have written more in detail, I'll try to do so now.
My main point was, that 'match("","")' should not return 0 (I tried to
emphasize this by enclosing 'not 0' in asterisks. Besides, there are
some "or"s in that sentence. I just mentioned returning 1 as one of
several theoretical possibilities, if we only look at this 'match("","")'
example. Returning 1 for any 'match("",...)' isn't a good idea at all,
as especially Irv previously had pointed out very clearly. I had agreed
to that, and in the light of the previous discussion, I didn't think it
was necessary to emphasize it again.
> In real life, the two characters that make up the null ""
> appear as simply:
>
> ""
>
> so if you happen so spot two more, like this:
>
> ""
>
> it is very logical to say that you have found the EXACT
> same thing in the second instance as the first (above).
> To enumerate this, we could say we have found exactly one
> of these 'things' and so it would make sense to assign the
> number 1 to this circumstance.
>
> On the computer, however, it's a very different world.
> First off, we our operating within the context of a
> programming language, which has to meet certain criteria
> which is different then that in the most basic, real life
> situtation.
I totally agree. That's why I didn't mention any 'real life example',
but the fact, that *in Euphoria* equal("","") = 1.
> For one thing, we have to be consistant in whatever we do,
> or the language will have a lot of anomalies and it will
> be hard to use.
Yes, that's what I wrote.
equal("","") = 1 -- as it is now (and hopefully will remain
-- in the future)
isn't consistent with
match("","") = 0 -- what you are suggesting
If any two sequences x and y are identical, i.e. if
equal(x,y) = 1
IMHO there shouldn't be returned 0 for
match(x,y).
By trying to improve the language, you are adding a new anomaly.
That -- and nothing else -- was exactly my point.
Now following my suggestion,
match("","")
either should return -1, or raise an error. Someone (you?) previously
wrote, that returning -1 would break too much existing code.
So the best solution probably would be: Just let match() alone.
> Granted, Euphoria has some of these already,
> that's why we ended up discussing this issue, but the idea
> is to REDUCE the number of anomalies over time in order to
> perfect the language.
> How do we accomplish this?
Certainly not by adding new anomalies.
> The answer lies in discovering how the individual functions
> work as a whole, and determining which ones dont quite fit
> in as well.
>
> In this case, we are talking about the function match, which
> has to work with two sequences, and has to return a value that
> is commensurate with the code that will follow, as well as with
> other functions that use sequences.
>
> The other interesting thing about match though, is that it
> is basically searching for something, within a sequence.
> If it finds something, it returns a number from 1 to max integer.
> If it doesnt find anything, it returns a zero.
>
> Let me repeat that last line one more time:
>
> "If it doesnt find anything, it returns a zero."
>
>
> Now in the real world, when we find
> ""
> we have indeed found something, but in the Euphoria language
> when we find
> ""
> we have not found anything
> (unless it is nested inside of another sequence such as {""} ).
>
> The evidence for this lies in looking at other functions
> that use sequences.
["d" is SOMETHING]
Agreed.
["" is clearly not SOMETHING]
Agreed.
> So you see, although we have no trouble finding "" in the real world,
> perhaps in a page of text, we do have trouble finding it within a
> first level sequence that already exists in the Euphoria language.
>
>
> Now back to the match function...
>
> We found out that "" is not SOMETHING in Euphoria, it is NOTHING,
> so we cant ever hope to find it within a one level sequence.
> This means
>
> match("","")
>
> is the same as
>
> match("",s)
>
> because we wont ever find anything if we are looking for nothing.
>
> Side note:
> If we are looking though a multi level sequence
> such as {"abc","",{""}}
> match has to return a zero because of a different reason,
> namely, because the search level is different.
>
>
> If you want to assume that if you are looking though nothing in hopes
> of finding nothing and you do indeed find nothing (because after all,
> if you find nothing havent you actually found it?), that you have
> actually found something because you have found nothing, then you can
> see that this still defaults to having found NOTHING!
> The reason for this is that when you look for nothing,
> it's just an idea, not a concrete object.
>
> Not only that, in real life
> you cant actually even get as far as to look for nothing, because then
> you could say you were actually looking for something, which you werent.
> On the computer however, this isnt true, because we can actually look
> for nothing because although nothing really doesnt exist, it still has
> a representation.
>
>
> Also, as i said before, returning 0 from
>
> match("",s)
>
> where s is ANY sequence, doesnt break any existing code,
> whereas every other idea i've heard so far does, no matter
> how good (or bad) it sounded.
>
> One advantage is that you can use the line
> while match(...)
> whereas right now you cant, unless you can also make sure
> the first sequence will never be null.
>
>
> I've understood your arguements, now try to understand mine.
Of course I tried it, but I think you didn't understand my arguments.
You again and again wrote something about 'real life' etc., thereby
verbose trying to refute arguments, that I never wrote.
On the other hand, you didn't go into the only argument that I wrote.
I agree to anything that you wrote, but your mail wasn't really a reply
to my previous post.
> Take care for now,
> Al
Best regards,
Juergen
--
/"\ ASCII ribbon campain |
\ / against HTML in | This message has been ROT-13 encrypted
X e-mail and news, | twice for higher security.
/ \ and unneeded MIME |
13. Re: match()
Hi Al, you wrote:
<big snip>
> Any more ideas or opinions now?
No.
> Perhaps we should go back to the more important issue of the
> namespace prefix 'fixes'?
I agree, that this is much more important. But I just wanted to mention
one or two ideas about namespaces that had occurred to me. A deep
discussion of that issue is above my head. I just hope that people with
more programming knowledge and experience than me, will find a simple,
flexible, powerful, and reliable (in one word "euphoric" solution.
> Take care for now,
> Al
Best regards,
Juergen
--
/"\ ASCII ribbon campain | |\ _,,,---,,_
\ / against HTML in | /,`.-'`' -. ;-;;,_
X e-mail and news, | |,4- ) )-,_..;\ ( `'-'
/ \ and unneeded MIME | '---''(_/--' `-'\_)
