The return value of s/// is the same as $/
If you want the resulting string instead you can use S/// instead.
> $_ = 'abc'
> my $r = S/b/./
> say $r
a.c
Note that it warns you try to use S/// with ~~
> my $r = 'abc' ~~ S/b/./
Potential difficulties:
Smartmatch with S/// is not useful. You can use given instead: S///
given $foo
------> my $r = 'abc' ~~ ⏏S/b/./
False
Which gives you an indicator of how to fix it
> my $r = S/b/./ given 'abc'
a.c
Note that the `given` happens before the `=`
So it works the same as
> my $r = ( S/b/./ given 'abc' )
a.c
---
The reason ~~ doesn't work with S/// has to do with the dual pass nature of
~~.
Without getting into details, you can avoid that by delaying the S/// until
the second pass.
> my $r = 'abc' ~~ { S/b/./ }
a.c
Or you can just set $_ to the value.
(Which is basically what the previous line is doing.)
> my $r = S/b/./ given 'abc'
> given 'abc' {
> my $r = S/b/./
> …
> }
> my $_ = 'abc'
> my $r = S/b/./
> my $r = 'abc' ~~ -> $_ { S/b/./ }
> my $r = 'abc' ~~ sub ( $_ ) { S/b/./ }
> my $r = 'abc' ~~ anon sub foo ( $_ ) { S/b/./ }
---
One of design goals of Raku is to have as few special cases as possible.
Which is why ~~ and S/// haven't been made to just work.
(It could be argued that in this case an exception could be made. But I'm
not going to argue for it.)
On Fri, Dec 6, 2019 at 10:37 PM William Michels via perl6-users <
perl6-us...@perl.org> wrote:
> Hello All,
>
> Todd put up some interesting code yesterday using the Raku/Perl6 REPL,
> which I reproduced with no problem. Additionally I tried some
> variations removing and/or moving parentheses to a different location,
> and have numbered the relevant REPL lines 1 through 6:
>
> mbook:~ homedir$ perl6
> To exit type 'exit' or '^D'
> 1> my $x = Q[word</b><br>] ;
> word</b><br>
> 2> (my $y = $x) ~~ s/ '<' .* //; say $/; say $x; say $y;
> ｢</b><br>｣
> word</b><br>
> word
> 3> my $a = Q[word</b><br>] ;
> word</b><br>
> 4> my $b = ($a ~~ s/ '<' .* //); say $/; say $a; say $b;
> ｢</b><br>｣
> word
> ｢</b><br>｣
> > my $c = Q[word</b><br>] ;
> word</b><br>
> > my $d = $c ~~ s/ '<' .* //; say $/; say $c; say $d;
> ｢</b><br>｣
> word
> ｢</b><br>｣
> 7> $*VM
> moar (2019.07.1)
>
> Working in groups of 2, lines 1 and 2 replicate the code Todd put up
> (parenthesis surrounding everything to the left of the smartmatch
> operator). I get the same result as Todd. What interests me are lines
> 3 through 6. Lines 3 and 4 are the virtually the same code but with
> parentheses surrounding everything to the right hand side (RHS) of the
> assignment operator (" = "). As people will note, lines 2 and lines 4
> give different results. Removing parentheses entirely in line 6 gives
> the same result as in line 4. Because the results in line 4 and line 6
> are the same, this says that as far as parentheses are concerned, the
> smartmatch operator "~~" takes precedence over the assignment operator
> "=".
>
> What's not clear to me in the code above (lines 4 and 6) is why
> variables $b and $d get assigned to $/. I would have expected in line
> 4 that $a would have been matched against the smartmatch, and the
> result ("word") would have been simply copied into variable $b. Have I
> misunderstood?
>
> Anyway, I'm just hoping to start a conversation on the topic of
> precedence in general, and hopefully getting some feedback as to where
> to look in the docs for further instruction.
>
> Best Regards, Bill.
>
>
> On Fri, Dec 6, 2019 at 12:15 AM ToddAndMargo via perl6-users
> <perl6-us...@perl.org> wrote:
> >
> > On 2019-12-05 23:19, ToddAndMargo via perl6-users wrote:
> > > On 2019-12-05 03:09, William Michels via perl6-users wrote:
> > >> What happens when you type "perl6" or "raku" at the bash command
> prompt?
> > >
> > > Hi William,
> > >
> > > On my shop machine, it jumps to the next line with an
> > > empty flashing cursor
> > >
> > > On my office machine, it told me to install
> > > zef install Readline
> > >
> > > After that, I get:
> > >
> > > $ perl6
> > > To exit type 'exit' or '^D'
> > > >
> > >
> > > and
> > >
> > > > say "hello World"
> > > hello World
> > > > say "B" ~ Q[:\] ~ " drive dismounted"
> > > B:\ drive dismounted
> > > >
> > >
> > > and sticking an obvious booboo into it
> > >
> > > > if 3 % 2 = 1 {say "odd"};
> > > Cannot modify an immutable Int (1)
> > > in block <unit> at <unknown file> line 1
> > >
> > > Plus I can use the arrow keys to recall previous lines too.
> > >
> > > Time up update my Perl6 on my shop computer!
> > >
> > > No more hassling with `perl6 -e` !!!
> > >
> > > Dude! THANK YOU !!!!!!
> > >
> > > -T
> >
> > You've created a monster!!
> >
> > perl6
> > To exit type 'exit' or '^D'
> > > my $x = Q[</b><br>]
> > </b><br>
> > > say $x
> > </b><br>
> > > (my $y = $x ) ~~ s/ Q[<] .* //;
> > ===SORRY!=== Error while compiling:
> > Unrecognized regex metacharacter < (must be quoted to match literally)
> > ------> (my $y = $x ) ~~ s/ Q[<] .* //;
> > > my $x = Q[abc</b><br>]
> > abc</b><br>
> > > (my $y = $x ) ~~ s/ '<' .* //;
> > ｢</b><br>｣
> > > (my $y = $x ) ~~ s/ '<' .* //; say $y
> > abc
> > > (my $y = $x ) ~~ s/ '<' .* //; say $x; say $y
> > abc</b><br>
> > abc
> >
> >
> > Thank you!
> >
> >
> > --
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > Computers are like air conditioners.
> > They malfunction when you open windows
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
