S04 mentions that statement modifiers behave as for perl5 (excpet that
you can have both an conditional modifier and a looping modifier on a
single statement.
Both then it gives this example, with be modifiers being operators
within an expression, not as modifiers of a statement.
line 260
The text of S02, S03, and S04 still contain references to the
now-defunct statement_modifier grammatical category.
Also, what's the reasoning behind specifically disallowing _all_
statement modifiers to do blocks (as opposed to forbidding just
looping statement modifiers)? Is this legacy from
/Perl-6.0.0-STD.pm
settles down.
: Also, what's the reasoning behind specifically disallowing _all_
: statement modifiers to do blocks (as opposed to forbidding just
: looping statement modifiers)? Is this legacy from when the
: distinction wasn't being made, or is there still a valid reason
Larry Wall wrote:
Jonathan Lang wrote:
: Larry Wall wrote:
: : Finally: when used as a statement modifier, is given considered to
: : be conditional or looping? (Gut instinct: conditional.)
:
: Why does it have to be one or the other? It's just a topicalizer.
:
: One implication of replacing
On 10/3/06, Aaron Sherman [EMAIL PROTECTED] wrote:
Paul Seamons wrote:
It relates to some old problems in the early part of the RFC/Apocalypse
process, and the fact that:
say $_ for 1..10 for 1..10
Was ambiguous. The bottom line was that you needed to define your
parameter name for
Damian Conway skribis 2006-10-03 16:40 (-0700):
Which can also be written as:
do { do { say 1 if 1 } if 1 } if 1;
Sorry, no it can't. From S4
(http://dev.perl.org/perl6/doc/design/syn/S04.html#The_repeat_statement):
Unlike in Perl 5, applying a statement modifier to a do block is
On 10/4/06, Juerd [EMAIL PROTECTED] wrote:
Damian Conway skribis 2006-10-03 16:40 (-0700):
Which can also be written as:
do { do { say 1 if 1 } if 1 } if 1;
Sorry, no it can't. From S4
(http://dev.perl.org/perl6/doc/design/syn/S04.html#The_repeat_statement):
Unlike in Perl 5,
It may be more useful to discuss this issue using less contrived
examples. :)
I would agree. I haven't had any use for a double if or a double for.
The double if case is handled by . The double for case is handled
by for and map.
The interesting cases are combinations of if and for and
:
perhaps a sentence to that effect belongs in S04, which has no mention
of nested statement modifiers, for or against.
Well, that's because Synopses at least in theory only refer to changes
from Perl 5. Perl 5 doesn't allow more than one statement modifier, and
Perl 6 doesn't either.
In Perl 5
Of course, that wasn't exactly what you were asking, but it does present
a practical solution when you want to:
{say $_ for =}.() if $do_read_input;
Which I just verified works fine under current pugs.
Thank you.
Hadn't thought of that. I think that is workable.
But it also brings
Paul Seamons wrote:
Of course, that wasn't exactly what you were asking, but it does present
a practical solution when you want to:
{say $_ for =}.() if $do_read_input;
Which I just verified works fine under current pugs.
Thank you.
Hadn't thought of that. I think that is workable.
have to parse the expression without knowing
what the parameters are, which is ugly in a very non-stylistic sense.
Again, thank you for your reply.
I don't think that is ambiguous though. If you view statement modifiers in
their unwrapped state, that example isn't any more ambiguous than
Paul Seamons wrote:
It relates to some old problems in the early part of the RFC/Apocalypse
process, and the fact that:
say $_ for 1..10 for 1..10
Was ambiguous. The bottom line was that you needed to define your
parameter name for that to work, and defining a parameter name on a
Aaron Sherman skribis 2006-10-03 13:46 (-0400):
In Perl 6, that's simplified to:
{{say 1 if 1}.() if 1}.() if 1;
Which can also be written as:
do { do { say 1 if 1 } if 1 } if 1;
Which if crammed together the way you wrote it, turns into:
do {do {say 1 if 1} if 1} if 1;
Or perhaps
Juerd wrote:
Which can also be written as:
do { do { say 1 if 1 } if 1 } if 1;
Sorry, no it can't. From S4
(http://dev.perl.org/perl6/doc/design/syn/S04.html#The_repeat_statement):
Unlike in Perl 5, applying a statement modifier to a do block is
specifically disallowed
Which if
[Apologies for the last post. Gmail got a little eager.
Here's what I meant to send...]
Juerd wrote:
Which can also be written as:
do { do { say 1 if 1 } if 1 } if 1;
Sorry, no it can't. From S4
(http://dev.perl.org/perl6/doc/design/syn/S04.html#The_repeat_statement):
Unlike in
在 Oct 4, 2006 7:46 AM 時，Damian Conway 寫到：
[Apologies for the last post. Gmail got a little eager.
Here's what I meant to send...]
Juerd wrote:
Which can also be written as:
do { do { say 1 if 1 } if 1 } if 1;
Sorry, no it can't. From S4
(http://dev.perl.org/perl6/doc/design/syn/
Audrey asked:
However, I wonder if this is too strict. Disallowing while and
until after a do block is fine (and can be coded directly in those
two statement modifier macros), but is there a reason to disallow
other modifiers?
Well, for a start, there's this syntactic problem:
do { say
go away. So indeed,
disallowing statement modifiers after do{} altogether seems sane.
Thanks!
Audrey
The use case here is
do { .foo for @bar } if $baz;
But I guess you can always protect it with a parens:
(do { .foo for @bar }) if $baz;
Or just:
if $baz { .foo for @bar }
or even:
@bar».foo if $baz;
;-)
Damian
Paul == Paul Seamons [EMAIL PROTECTED] writes:
Paul I don't know what the reasoning was back then and it may be the same
today.
From my early conversations with Larry, I recall that the reason is that
RSTS/E BASIC-PLUS had nested trailing modifiers, and both Larry and I saw many
abuses of
Paul Seamons schreef:
In the samples you gave I had to read the entire line to see
what the outcome of the code is.
I was not addressing reading skills, but just your you'd either have
... or One always needs to read the full line, but one doesn't
have to do that linearly or just from
From my early conversations with Larry, I recall that the reason is that
RSTS/E BASIC-PLUS had nested trailing modifiers, and both Larry and I saw
many abuses of these over the years. Therefore, he decided not to repeat
that abomination, limiting it to precisely one level deep. I'm happy for
I will abuse it.
Paul
PS. And not that it matters, but TT3 is planned to support nested statement
modifiers and my engine which does much of TT3 already supports them - and I
do use them on occasion - but that's a different mailing list.
On Wed, Aug 30, 2006 at 01:37:33PM +0800, Agent Zhang wrote:
: Hi, there~
:
: I think S04 says too little about statement modifiers. Please comment
: on the following code samples. Are they valid Perl 6?
:
:do { say } for 1..3;
The do-BLOCK construct does not allow statement modifiers
I'm not sure if I have seen this requested or discussed.
Is there a parsing reason why Perl 6 would allow nested statement modifiers or
is it mainly a sanity-please-don't-hurt-my-eyes reason.
It is silly to do things such as:
say Interesting if $just_because if $because;
But it is sort
In a message dated Fri, 1 Sep 2006, Paul Seamons writes:
I'm not sure if I have seen this requested or discussed.
This was definitively rejected by Larry in 2002:
http://www.nntp.perl.org/group/perl.perl6.language/9343
He has not revisited the issue in the several times it has come up
the issue in the several times it has come up since.
perhaps a sentence to that effect belongs in S04, which has no mention
of nested statement modifiers, for or against.
~jerry
/group/perl.perl6.language/9343
He has not revisited the issue in the several times it has come up since.
perhaps a sentence to that effect belongs in S04, which has no mention
of nested statement modifiers, for or against.
Well, that's because Synopses at least in theory only refer to changes
) of the Perl 6 grammar have changed and reverted and
changed again.
I don't know what the reasoning was back then and it may be the same today.
I'm just wondering what that reason is. Maybe nested statement modifiers
promote bad language skills. Maybe its because statement modifiers have
always
Paul Seamons schreef:
The following is one more interesting case.
say Ok then if $yes and $true unless $no or $false;
Without nested modifiers you'd have either:
say Ok then if $yes and $true and ! $no and ! $false;
or
say OK then unless ! $yes or ! $true or $no $or $false;
And
$no or $false or $yes and $true and say OK then ;
$no or $false or say OK then if $yes and $true ;
Thank you for your reply.
I know there are other ways to do it. I've had no choice but to do it other
ways in Perl5.
I don't think I have ever used that notation (outside of file open and
Hi, there~
I think S04 says too little about statement modifiers. Please comment
on the following code samples. Are they valid Perl 6?
do { say } for 1..3;
{ say } for 1..3;
- $i { say $i } for 1..3;
And how about similar variations for other statement modifiers, such
as while
to [not] add a Cwhere statement modifier which restricts
: the scope of the declarations?
Already used where for subtype constraints.
: Sure its redundant, but so are all
: statement modifiers. Sometimes its good to factor things out and express
: them later, rather than earlier. It lets us focus
of the declarations? Sure its redundant, but so are all
statement modifiers. Sometimes its good to factor things out and express
them later, rather than earlier. It lets us focus on the important
things first:
print $a $b $c where ($a,$b,$c)=(1,2,3);
(in this case, we could use printf to to the factoring
extrapolation.
I guess to be honestly consistent all modifiers would have to become
operators, which would bring us back to the multiple statement modifiers
to which Larry said no..
I'll rest my case
--
Matthijs van Duin -- May the Forth be with you!
I just read Piers' summary:
Matthijs van Duin wondered if the issue of multiple statement modifiers
has been settled. The thread is long, and the answer is essentially (and
authoritatively) Yes, it's settled. No, you can't do it. So, unless
Larry changes his mind the point is moot.
So apparently I
To save people from having to re-read the thread, here is the actual
proposal in detail again:
PROPOSAL
Replace the 'if', 'unless', 'when' statement modifiers by identically
named lowest-precedence left-associative operators that short-circuit
from right to left.
This means
[EMAIL PROTECTED] (Luke Palmer) writes:
we have a definitive
^^
Remember that this is Perl 6. You keep using that word, etc.
--
void russian_roulette(void) { char *target; strcpy(target, bullet); }
Simon Cozens:
# [EMAIL PROTECTED] (Luke Palmer) writes:
# we have a definitive
# ^^
# Remember that this is Perl 6. You keep using that word, etc.
It *is* definitive, Simon...at least this week. ;^)
--Brent Dax [EMAIL PROTECTED]
@roles=map {Parrot $_} qw(embedding regexen
of multiple statement modifiers
already been settled? I saw some mention it wasn't going to be supported,
but also mentions of how it would be useful; I can think of such a
situation myself:
.method when MyClass given $obj;
as alternative to:
$obj.method if $obj.isa(MyClass);
except without
--- Matthijs van Duin [EMAIL PROTECTED] wrote:
Now the real subject.. has the issue of multiple statement modifiers
already been settled? I saw some mention it wasn't going to be
supported, but also mentions of how it would be useful; I can think
of such a situation myself:
.method when
On Mon, Mar 10, 2003 at 08:20:39AM -0800, Paul wrote:
The real nightmare tends to show up when you duplicate a modifier.
What does
.method given $x given $y; # which object's .method is called?
mean? It gets worse below
I made a mistake in my original post, they definitely need to be left-
PROPOSAL
Replace the 'if', 'unless', 'when' statement modifiers by identically
named lowest-precedence left-associative operators that short-circuit
from right to left.
This means 'FOO if BAR' is identical to 'BAR and FOO', except it has a
lower precedence, and 'FOO unless BAR
On Mon, Mar 10, 2003 at 01:14:05PM -0700, Luke Palmer wrote:
It is nice to see someone who puts as much thought into posting as you
do. Unfortunately, your proposal is moot, as we have a definitive
No, still can't chain them from Larry.
On Wed, 2002-04-03 at 20:49, Larry Wall wrote:
: Additionally, can you chain statement modifiers?
:
: do_this() if $a unless $b;
[...]
No, still can't chain them.
That's a darned shame. In p5, I keep going back to code and finding
something like:
print foreach x;
and wanting
So, does the new =~ commute now, except for regexps; i.e.
$a =~ $b
is the same as
$b =~ $a
unless one or both are regexps?
Additionally, can you chain statement modifiers?
do_this() if $a unless $b;
print for mylist if $debug;
or less efficiently,
print if $debug for mylist;
print $x
Luke Palmer writes:
: So, does the new =~ commute now, except for regexps; i.e.
:
: $a =~ $b
: is the same as
: $b =~ $a
:
: unless one or both are regexps?
I believe I marked which ones commute in A4.
: Additionally, can you chain statement modifiers?
:
: do_this() if $a unless $b;
: print
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