Re: Proposal: split ternary ?? :: into binary ?? and //
[EMAIL PROTECTED] (Larry Wall) writes: So let's go ahead and make it ??!!. (At least this week...) I hereby christen this the interrobang operator. (http://en.wikipedia.org/wiki/Interrobang) -- Your fault: core dumped -- MegaHAL
Re: Proposal: split ternary ?? :: into binary ?? and //
On Tue, Sep 06, 2005 at 04:57:30PM +0200, Thomas Sandlass wrote: : HaloO, : : Luke wrote: : Okay, now why don't you tell us about this new binary :: you're proposing. : : Well, not a new one. Just plain old foo::bar::blahh and 'my ::blubb $x' : with relaxed whitespace rules. The ternary ?? :: is a splinter in my : mind's eye because it is not a compile time or symbol lookup construct. : : The driving idea is to let tokens always mean the same or at least very : similar things in different contexts. And I thought that is your rating : as well. For :: that should be 'symbol table management'. E.g. ::= fits : that notion perfectly while the alternative separation of the ternary : doesn't. I think that's a powerful argument even if we don't have an infix:::. Plus I hate all infix nor operators due to my English-speaking bias that requires a neither on the front. So let's go ahead and make it ??!!. (At least this week...) Larry
Re: Proposal: split ternary ?? :: into binary ?? and //
On Wed, Sep 07, 2005 at 08:32:39AM -0700, Larry Wall wrote: I think that's a powerful argument even if we don't have an infix:::. Plus I hate all infix nor operators due to my English-speaking bias that requires a neither on the front. So let's go ahead and make it ??!!. (At least this week...) Yay !! Pm
Re: Proposal: split ternary ?? :: into binary ?? and //
Larry Wall skribis 2005-09-07 8:32 (-0700): I think that's a powerful argument even if we don't have an infix:::. Plus I hate all infix nor operators due to my English-speaking bias that requires a neither on the front. So let's go ahead and make it ??!!. (At least this week...) I was going to object based on !!foo being ! ! foo, but that !! is spelled ? now, so nevermind. Juerd -- http://convolution.nl/maak_juerd_blij.html http://convolution.nl/make_juerd_happy.html http://convolution.nl/gajigu_juerd_n.html
Re: Proposal: split ternary ?? :: into binary ?? and //
Luke wrote: Not that being explicit is always a bad thing: $val = some_cond() ?? ($arg1 // $arg1_default) // ($arg2 // $arg2_default) No. What's a bad thing is creating new linguistic traps for when people inevitably forget to be explicit. And I question your notion of highly useful in this case. Huh??? Both // and the ternary are unquestionably highly useful constructs. My point was that making them not work together is a Very Bad Idea. I guess the thing that I really think is nice is getting :: out of that role and into the type-only domain. Yes, I'd certainly like that too. But not at the cost of turning // into a bear-pit for the unsuspecting. Damian
Re: Proposal: split ternary ?? :: into binary ?? and //
On Tue, Sep 06, 2005 at 07:26:37AM +1000, Damian Conway wrote: Thomas Sandlass wrote: I'm still contemplating how to get rid of the :: in the ternary Comments? I believe that the single most important feature of the ternary operator is that it is ternary. That is, unlike an if-else sequence, it's impossible to leave out the else in a ternary operation. Splitting the ternary destroys that vital characteristic, which would be a very bad outcome. At OSCON I was also thinking that it'd be really nice to get rid of the :: in the ternary and it occurred to me that perhaps we could use something like '?:' as the 'else' token instead: (cond) ?? (if_true) ?: (if_false) However, I'll freely admit that I hadn't investigated much further to see if this might cause other syntax ambiguities. Pm
RE: Proposal: split ternary ?? :: into binary ?? and //
HaloO, Luke wrote: ?? !! ain't bad either. It's definitely much better that sabotaging the (highly useful) // operator within (highly useful) ternaries. I guess the thing that I really think is nice is getting :: out of that role and into the type-only domain. Right. To make :: indicate type or meta was my primary concern. So I see the following situation: unwanted ?? :: ASCII replacements ?? //# two binaries ?? \\# I would like it as chaining binary nor ?? !!# wasn't binary ! the none() constructor # and !! the binary nor---at least in Pugs? Latin1 replacements ?? ¦¦ ?? ¡¡ ?? ¿¿ @Larry's choice? -- TSa
Re: Proposal: split ternary ?? :: into binary ?? and //
On 9/6/05, Thomas Sandlass [EMAIL PROTECTED] wrote: Right. To make :: indicate type or meta was my primary concern. Okay, now why don't you tell us about this new binary :: you're proposing. Luke
RE: Proposal: split ternary ?? :: into binary ?? and //
HaloO, Luke wrote: Okay, now why don't you tell us about this new binary :: you're proposing. Well, not a new one. Just plain old foo::bar::blahh and 'my ::blubb $x' with relaxed whitespace rules. The ternary ?? :: is a splinter in my mind's eye because it is not a compile time or symbol lookup construct. The driving idea is to let tokens always mean the same or at least very similar things in different contexts. And I thought that is your rating as well. For :: that should be 'symbol table management'. E.g. ::= fits that notion perfectly while the alternative separation of the ternary doesn't. There's yet another approach, to make ternary listfix: $val = $cond ?? true ?? false; and perhaps we change it from ternary to (n 2)-ary: $val = $tested_only ?? $val_or_test ?? $other_or_test ?? $final; But in both ways, recursive ternary needs parens. Which can be regarded as a good thing. This listfix ?? behaves more like a rhs returning ||. As the RegularityGuy(TM) I like the chaining triple // || \\ where // returns the first defined, || returns the first true and \\ returns the first false. And of course there are low precedence counterparts err, or, nor. And the binary \ for none() construction. BTW is (\) indicating the relative complement of the set operators? Even the unary ref prefix makes sense as \ because it means 'not the value' or 'not right here but keep for later reference'. -- TSa
Re: Proposal: split ternary ?? :: into binary ?? and //
On Tue, Sep 06, 2005 at 04:57:30PM +0200, Thomas Sandlass wrote: There's yet another approach, to make ternary listfix: $val = $cond ?? true ?? false; So ^^ that one doesn't do the same thing as ^^ that one? I'd find that confusing in itself. And that's without considering the change from the C? : of C and Perl 5. [contents of this message may settle in transit, particularly if your mail reader uses a proportional font.] Nicholas Clark
Proposal: split ternary ?? :: into binary ?? and //
HaloO,
I'm still contemplating how to get rid of the :: in the
ternary and make :: unequivocally available for a type
sigil and as a binary infix for symbol lookup.
Here's a possible solution:
1) ?? becomes a binary operator that behaves as follows:
a) it evaluates its lhs in boolean context
b) if this is true, ?? evaluates its rhs such that it
can't be undef
c) if this is false, ?? returns undef
2) the precedence of ?? is above // which naturally catches
the undef of a false condition.
This gives
$x = $y 3 ?? small // large;
and possibly even a low precedence version
$x = $y 3 then small err large; # hmm
thence # old fashioned
therefore # long, but clear
An implementation could read:
*infix:?? (cond, code)
is parsed(...) # trait needed to insert {}?
{
if cond() { return code() but defined }
else { return undef }
}
Comments?
TSa
Re: Proposal: split ternary ?? :: into binary ?? and //
Thomas Sandlass skribis 2005-09-05 14:38 (+0200): b) if this is true, ?? evaluates its rhs such that it can't be undef But $foo ?? undef // 1 then is a problem. Juerd -- http://convolution.nl/maak_juerd_blij.html http://convolution.nl/make_juerd_happy.html http://convolution.nl/gajigu_juerd_n.html
Re: Proposal: split ternary ?? :: into binary ?? and //
Thomas Sandlass wrote: I'm still contemplating how to get rid of the :: in the ternary Comments? I believe that the single most important feature of the ternary operator is that it is ternary. That is, unlike an if-else sequence, it's impossible to leave out the else in a ternary operation. Splitting the ternary destroys that vital characteristic, which would be a very bad outcome. Damian
Re: Proposal: split ternary ?? :: into binary ?? and //
Patrick suggested: At OSCON I was also thinking that it'd be really nice to get rid of the :: in the ternary and it occurred to me that perhaps we could use something like '?:' as the 'else' token instead: (cond) ?? (if_true) ?: (if_false) However, I'll freely admit that I hadn't investigated much further to see if this might cause other syntax ambiguities. I think the main problem there would be the *visual* similarity between the two. Damian
Re: Proposal: split ternary ?? :: into binary ?? and //
On 9/5/05, Damian Conway [EMAIL PROTECTED] wrote: Patrick suggested: At OSCON I was also thinking that it'd be really nice to get rid of the :: in the ternary and it occurred to me that perhaps we could use something like '?:' as the 'else' token instead: (cond) ?? (if_true) ?: (if_false) However, I'll freely admit that I hadn't investigated much further to see if this might cause other syntax ambiguities. I think the main problem there would be the *visual* similarity between the two. Indeed. The logical (bad pun intended) operator to match with ?? is !! (cond) ?? (if_true) !! (if_false) Ashley Winters
Re: Proposal: split ternary ?? :: into binary ?? and //
On 9/5/05, Juerd [EMAIL PROTECTED] wrote: Thomas Sandlass skribis 2005-09-05 14:38 (+0200): b) if this is true, ?? evaluates its rhs such that it can't be undef But $foo ?? undef // 1 then is a problem. Yeah. Hmm, but I kinda like the look of ?? //, and I don't like the overloading of :: in that way anymore. So it's possible just to add a ternary ?? // in addition to, and unrelated to (from the parser's perspective), the regular //. ?? !! ain't bad either. Luke
Re: Proposal: split ternary ?? :: into binary ?? and //
Luke wrote: Yeah. Hmm, but I kinda like the look of ?? //, and I don't like the overloading of :: in that way anymore. So it's possible just to add a ternary ?? // in addition to, and unrelated to (from the parser's perspective), the regular //. Bad idea. This useful construct would then be ambiguous: $val = some_cond() ?? $arg1 // $arg1_default // $arg2 // $arg2_default; ?? !! ain't bad either. It's definitely much better that sabotaging the (highly useful) // operator within (highly useful) ternaries. Damian
Re: Proposal: split ternary ?? :: into binary ?? and //
On 9/6/05, Damian Conway [EMAIL PROTECTED] wrote: Luke wrote: Yeah. Hmm, but I kinda like the look of ?? //, and I don't like the overloading of :: in that way anymore. So it's possible just to add a ternary ?? // in addition to, and unrelated to (from the parser's perspective), the regular //. Bad idea. This useful construct would then be ambiguous: $val = some_cond() ?? $arg1 // $arg1_default // $arg2 // $arg2_default; Huh, yeah. We'd have to go one way or the other on that, and neither of those are what you intend. Not that being explicit is always a bad thing: $val = some_cond() ?? ($arg1 // $arg1_default) // ($arg2 // $arg2_default) And I question your notion of highly useful in this case. Still, it is probably linguistically not a good idea to overload // like that. ?? !! ain't bad either. It's definitely much better that sabotaging the (highly useful) // operator within (highly useful) ternaries. I guess the thing that I really think is nice is getting :: out of that role and into the type-only domain. Luke
