RE: General Feelings on Apoc 3
On Tue, 2001-10-09 at 22:42, Damian Conway wrote: Brent asked: If we have 'and', 'or' and 'xor', can we have 'dor' (defined or) to be a low-precedence version of this? I actually suggested exactly that to Larry a few weeks back. He likes the idea, but is having trouble finding an acceptable name for the operator. I think the time has come, at last, to suggest a new operator -- and perhaps this would be a good place for it. We need the 'doh' operator. And to borrow from another thread, we might even be able to say doh! ;-) David -- David Wheeler AIM: dwTheory [EMAIL PROTECTED] ICQ: 15726394 Yahoo!: dew7e Jabber: [EMAIL PROTECTED]
Re: General Feelings on Apoc 3
On Wed, 10 Oct 2001 15:42:29 +1000 (EST), Damian Conway wrote: Brent asked: If we have 'and', 'or' and 'xor', can we have 'dor' (defined or) to be a low-precedence version of this? I actually suggested exactly that to Larry a few weeks back. He likes the idea, but is having trouble finding an acceptable name for the operator. I'm not convinced it's that useful... The precedence of dor would be lower than that of assignment. And it's precisely in assignment where the // operator will come in very handy. If you don't need to assign the value of the expression, you can just as wel use defined(): defined($x = foo()) or die Got an undefined value!; Plus there's the matter of the name... Do we really need low and high precedence equivalents of every boolean operator? Next, you'll want a low precedence ?: (or ??::). We have one already: if/else, but except in do blocks, you can't really use them for expressions. -- Bart.
RE: General Feelings on Apoc 3
Bart Lateur: # On Thu, 4 Oct 2001 03:22:55 -0400, Michael G Schwern wrote: # # Binary // # # The analogy to || is probably a bit too clever. My first reaction # was it's some sort of weird division operator. But it's servicable. # # I think it's very cute. I think of it as a skewed or, which is, er, # both what it both is, and what it looks like. If we have 'and', 'or' and 'xor', can we have 'dor' (defined or) to be a low-precedence version of this? --Brent Dax [EMAIL PROTECTED] Configure pumpking for Perl 6 They *will* pay for what they've done.
Re: General Feelings on Apoc 3
On Tue, Oct 09, 2001 at 08:35:10AM -0700, Brent Dax wrote: Bart Lateur: # On Thu, 4 Oct 2001 03:22:55 -0400, Michael G Schwern wrote: # # Binary // # # The analogy to || is probably a bit too clever. My first reaction # was it's some sort of weird division operator. But it's servicable. # # I think it's very cute. I think of it as a skewed or, which is, er, # both what it both is, and what it looks like. If we have 'and', 'or' and 'xor', can we have 'dor' (defined or) to be a low-precedence version of this? I like dor. default also seems natural, but long. Then again, I don't think else is ever legal unless if appears between braces, so that's another possibility if we wish to recycle syntax. $live.happy else die Sad Looks pretty nice. Perhaps confusing if folks think else and or mean the same thing. If else seems to iffish, perhaps it could even be or else, which is also not currently legal, AFAIK $live.happy or else die Sad Hmm gets me thinking evil thoughts... like having else be the low-prec. //, and then or else be synonymous with ``else die $!'' so you get: $live.happy or else Read my lips: NO NEW TOKENS! ;-) -- Aaron Sherman [EMAIL PROTECTED] finger [EMAIL PROTECTED] for GPG info. Fingerprint: www.ajs.com/~ajs6DC1 F67A B9FB 2FBA D04C 619E FC35 5713 2676 CEAF Write your letters in the sand for the day I'll take your hand In the land that our grandchildren knew. -Queen/_'39_
Re: General Feelings on Apoc 3
Brent Dax wrote: If we have 'and', 'or' and 'xor', can we have 'dor' (defined or) to be a low-precedence version of this? Oh man. If we've gone so far as 'dor', why not make it 'doh' :-) print stomach_state @beer,@donuts doh burp!!! -- -- Tim Conrow [EMAIL PROTECTED] |
Re: General Feelings on Apoc 3
On Tue, Oct 09, 2001 at 11:49:15AM -0700, Tim Conrow wrote: Brent Dax wrote: If we have 'and', 'or' and 'xor', can we have 'dor' (defined or) to be a low-precedence version of this? Oh man. If we've gone so far as 'dor', why not make it 'doh' :-) print stomach_state @beer,@donuts doh burp!!! Well, that opens up a few possibilities... First of all, we'll want to have a unary defaulting operator. For example, $donuts should check the type of $donuts and do the same thing as $donuts is default The universal definition of default should return undef so that $donuts doh burp!!! Would do what you expect. In our next issue, I'll be getting into the intricacies of the chainable diddly-aye-o suffix operator -- Aaron Sherman [EMAIL PROTECTED] finger [EMAIL PROTECTED] for GPG info. Fingerprint: www.ajs.com/~ajs6DC1 F67A B9FB 2FBA D04C 619E FC35 5713 2676 CEAF Write your letters in the sand for the day I'll take your hand In the land that our grandchildren knew. -Queen/_'39_
RE: General Feelings on Apoc 3
Brent asked: If we have 'and', 'or' and 'xor', can we have 'dor' (defined or) to be a low-precedence version of this? I actually suggested exactly that to Larry a few weeks back. He likes the idea, but is having trouble finding an acceptable name for the operator. Damian
Re: General Feelings on Apoc 3
David M. Lloyd wrote: On Thu, 4 Oct 2001, Michael G Schwern wrote: Backtracking is at the heart of Logic Programming (or Declarative Programming, if you like). This is one of the 3 main programming paradigms (along with procedural and functional). The most popular Declarative language is Prolog. It is great for writing programs that are largely about resource allocation and constraints. There's some links to start you off here: http://foldoc.doc.ic.ac.uk/foldoc/foldoc.cgi?backtracking Sounds like a chess computer. It kind of struck me that this type of concept might be handy for writing parsers directly in Perl without an 'intermediate' parsing language. Or for making it easier to write such an intermediate language. Backtracking is typically not used in parser implementations because it's slow over other predictive techniques. It's needed in a few cases of highly ambiguous languages (e.g. LL-infinite parsers). Another idea : it should be possible to write makefile-like rules with backtracking.
Re: General Feelings on Apoc 3
I think this would be interesting for U :) http://www.cs.yorku.ca/Courses/3401/lectures/340198-11-27HTML/ http://www.cogs.susx.ac.uk/local/books/nlp-in-prolog/ch04/chapter-04-sh-1.5. html#sh-1.5 | On Thu, 4 Oct 2001, Michael G Schwern wrote: | | Backtracking is at the heart of Logic Programming (or Declarative | Programming, if you like). This is one of the 3 main programming paradigms | (along with procedural and functional). The most popular Declarative | language is Prolog. It is great for writing programs that are largely about | resource allocation and constraints. There's some links to start you off | here: | | http://foldoc.doc.ic.ac.uk/foldoc/foldoc.cgi?backtracking | | Sounds like a chess computer. | | It kind of struck me that this type of concept might be handy for writing | parsers directly in Perl without an 'intermediate' parsing language. Or | for making it easier to write such an intermediate language. | | - D | | [EMAIL PROTECTED] |
Re: General Feelings on Apoc 3
Thus it was written in the epistle of David Nicol, Michael G Schwern wrote: Binary ; This worries me. Giving ; two meanings makes basic language parsing harder, which would be fine if there was a big payoff, but there's not. Just making shorthand for [[1,2,3],[4,5,6]] doesn't seem worth it. What am I missing here? What you might be missing here (or what I might be improperly getting here) is that a good way to implement this sort of thing is with an exception handling parser. The end-of-statement-while-brackets-are-open error can be trapped and turned into More Useful Syntax. What worries me is that the end-of-statement-while-brackets-are-open error would be trapped and turned into a More Serious Problem. If, perchance, I'm not the only one to have Accidentally Omitted a Closing Bracket, there may be someone out there who prefers having the compiler object to the missing bracket rather than have it attempt to run the code, assuming that the ; is really *not* the end of the statement. 'Course, it has long been held that *any* random sequence of characters is a valid Perl program, and this makes that a little more true. Ted -- Ted Ashton ([EMAIL PROTECTED]) | From the Tom Swifty collection: Southern Adventist University| It doesn't seem one should sing nonsense Deep thought to be found at | syllables instead of words, said Ward http://www.southern.edu/~ashted | Swingle dubiously.
Re: General Feelings on Apoc 3
On Thu, Oct 04, 2001 at 05:59:53PM +1000, Damian Conway wrote: Hyperoperators: I sort of understand it, but don't really grok it. I can sort of thing of ways it might eliminate the need for a few maps and foreaches. Damian, might I request some clarification in Exogenesis? Well, I'll probably clarify them in Exegesis instead. External birth would seem a bit extreme here. ;-) Sorry, didn't mean to imply that you'd laid an egg. ;) Backtracking: Ok, I don't get it at all. Damian, clarification? Nothing to clarify. Larry punted (to a later Apocalypse). Okay. That's a cop-out. He's basically saying that you can write Candthen and Corthen yourself as: snip I understand that much. What I don't quite get is the utility. There's some hand-waving in the RFC about making parsers easier. -- Michael G. Schwern [EMAIL PROTECTED]http://www.pobox.com/~schwern/ Perl6 Quality Assurance [EMAIL PROTECTED] Kwalitee Is Job One Obscenity is the last resort of the illiterate, Mother Fucker -- KAL
Re: General Feelings on Apoc 3
On Thu, 4 Oct 2001, Michael G Schwern wrote: Backtracking is at the heart of Logic Programming (or Declarative Programming, if you like). This is one of the 3 main programming paradigms (along with procedural and functional). The most popular Declarative language is Prolog. It is great for writing programs that are largely about resource allocation and constraints. There's some links to start you off here: http://foldoc.doc.ic.ac.uk/foldoc/foldoc.cgi?backtracking Sounds like a chess computer. It kind of struck me that this type of concept might be handy for writing parsers directly in Perl without an 'intermediate' parsing language. Or for making it easier to write such an intermediate language. - D [EMAIL PROTECTED]
Re: General Feelings on Apoc 3
Backtracking:
Ok, I don't get it at all. Damian, clarification?
Nothing to clarify. Larry punted (to a later Apocalypse).
Okay. That's a cop-out. He's basically saying that you can write
Candthen and Corthen yourself as:
snip
I understand that much. What I don't quite get is the utility.
There's some hand-waving in the RFC about making parsers easier.
Parsing will not be the major application, I think.
To see the utility, you need to look at a language whether this feature
is already central to the language. Icon http://www.cs.arizona.edu/icon/
is a good example.
To see how backtracking might work in Perl, here's an program (adapted
to RFC 104 syntax) that prints out Pythagorean triangle triplets with
side-lengths less than 100:
$x=100;
{ $y=100; --$x }
andthen { $z=100; --$y }
andthen { { --$z } andthen { $x**2 == $y**2 + $z**2 } }
andthen { print $x, $y, $z\n; 0};
Incidentally, that's why Larry was musing over the idea of the left operand's
scope extending to the right operand. If that were the case, we could make $x,
$y, and $z safely lexical:
my $x=100;
{ my $y=100; --$x }
andthen { my $z=100; --$y }
andthen { { --$z } andthen { $x**2 == $y**2 + $z**2 } }
andthen { print $x, $y, $z\n; 0};
and the later blocks would still see them.
Personally, I think:
foreach my $x (1..99) {
foreach my $y (1..99) {
foreach my $z (1..99) {
print $x, $y, $z\n if $x**2 == $y**2 + $z**2;
}}}
is much cleaner.
But it certainly does demonstrate TMTOWTDI. ;-)
Damian
Re: General Feelings on Apoc 3
Or even
for my $x (1..98) {
for my $y (1..(99-$x)) {
for my $z (1..(100-$x-$y)) {
print $x, $y, $z\n if $x ** 2 = $y ** 2 + $z ** 2;
}
}
}
Sure. Depending on whether you want combinations or permutations.
Damian
Re: General Feelings on Apoc 3
Michael G Schwern wrote: Binary ; This worries me. Giving ; two meanings makes basic language parsing harder, which would be fine if there was a big payoff, but there's not. Just making shorthand for [[1,2,3],[4,5,6]] doesn't seem worth it. What am I missing here? What you might be missing here (or what I might be improperly getting here) is that a good way to implement this sort of thing is with an exception handling parser. The end-of-statement-while-brackets-are-open error can be trapped and turned into More Useful Syntax. Alternately, semicolon only means statement-end when all brackets are balanced. Suddenly we have more syntax to play with: an easy-to-find separator is no longer pinned into its one role as statement terminator, to use a chess metaphor. The list-of-lists is an example of what can be done; it is not the point of the innovation. Things like syntaces for declaring your named arguments come to mind as a more intense use of this feature. I am not caught up with the state of the art enough to produce a compliant example at this time. Binary // The analogy to || is probably a bit too clever. My first reaction was it's some sort of weird division operator. But it's servicable. It echoes the switch from | to / within the IETF RFC syntax declaration language. Apparently the global keyboard steering committee has deprecated the vertical bar. Hyperoperators: I sort of understand it, but don't really grok it. I can sort of thing of ways it might eliminate the need for a few maps and foreaches. Damian, might I request some clarification in Exogenesis? I am not Damian, but I'll try: The feature is not, IMO, big enough to warrant giving it the really-big-sounding name hyperoperator but it is as good as any and no other (?) language has it at this particular level of explicitness (overloads on C++ container classes notwithstanding.) There is no way to disambiguate the do-once case from the do-for-each case without some syntax of some kind, so hat-operator is pressed into the role. I suppose descent into LoL and attitude towards multidim is up to the operator getting hyperized -- that is a point for regularization of some kind, cultural if not linguistic. Backtracking: Ok, I don't get it at all. Damian, clarification? Me neither. I had thought that backtracking dealt with remembering one's side effects so they could be unwound. The RFC in question was completely incomprehensible to me as well, and possibly written by someone who was not aware that Perl's logical operators short-circuit by definition. What am I missing?
Re: General Feelings on Apoc 3
On Thu, Oct 04, 2001 at 08:29:10PM -0500, David Nicol wrote: Binary // The analogy to || is probably a bit too clever. My first reaction was it's some sort of weird division operator. But it's servicable. It echoes the switch from | to / within the IETF RFC syntax declaration language. Apparently the global keyboard steering committee has deprecated the vertical bar. You don't know how many times I've heard people complain that Perl isn't catering enough to the needs of IETF RFC authors. :-P I have a feeling that echoing the IETF is just a coincidence. -- Michael G. Schwern [EMAIL PROTECTED]http://www.pobox.com/~schwern/ Perl6 Quality Assurance [EMAIL PROTECTED] Kwalitee Is Job One purl Hey, Schwern! THERE IS A HUGE GAZORGANSPLATTEDFARTMONGERING- LIGHTENINGBEASTASAURSOPOD BEHIND YOU! RUN, BEFORE IT GAFLUMMOXES YOUR INNARDLYBITS!
Re: General Feelings on Apoc 3
Damian == Damian Conway [EMAIL PROTECTED] writes:
Damian Personally, I think:
Damian foreach my $x (1..99) {
Damian foreach my $y (1..99) {
Damian foreach my $z (1..99) {
Damian print $x, $y, $z\n if $x**2 == $y**2 + $z**2;
Damian }}}
Damian is much cleaner.
Or even
for my $x (1..98) {
for my $y (1..(99-$x)) {
for my $z (1..(100-$x-$y)) {
print $x, $y, $z\n if $x ** 2 = $y ** 2 + $z ** 2;
}
}
}
Damian But it certainly does demonstrate TMTOWTDI. ;-)
TMT2WTDI :-)
--
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