Re: regex: how to I pick out items in the middle?

[ToddAndMargo via perl6-users]

On 10/29/22 22:37, William Michels via perl6-users wrote:

On Sat, Oct 29, 2022 at 7:29 PM ToddAndMargo via perl6-users <perl6-us...@perl.org <mailto:perl6-us...@perl.org>> wrote:

     >> On Sat, Oct 29, 2022 at 6:46 PM ToddAndMargo via perl6-users
     >> <perl6-us...@perl.org <mailto:perl6-us...@perl.org>
    <mailto:perl6-us...@perl.org <mailto:perl6-us...@perl.org>>> wrote:
     >>
     >>     Hi All,
     >>
     >>     With a regex, how do I pick out items in the middle of the
    string?  Two
     >>     from the beginning or two from the end?
     >>
     >>
     >>     4] > my Str $y="xxxxxx"; $y ~~ s/ $([.*-2]) "x"/Q/; print $y
    ~ "\n"
     >>
     >>     ===SORRY!=== Error while compiling:
     >>     Malformed postfix call
     >>     ------> my Str $y="xxxxxx"; $y ~~ s/ $([.*⏏-2]) "x"/Q/;
    print $y ~ "\n"
     >>
     >>
     >>
     >>     I am trying to do something like this:
     >>
     >>     [0] > my Str $x="1\n2\n3\n4\n5\n"
     >>     1
     >>     2
     >>     3
     >>     4
     >>     5
     >>
     >>     [1] > print $x.lines[*-2] ~ "\n"
     >>     4

    On 10/29/22 19:16, William Michels via perl6-users wrote:
     > In the Raku REPL:
     >
     > $ raku
     > Welcome to Rakudo™ v2022.07.
     > Implementing the Raku® Programming Language v6.d.
     > Built on MoarVM version 2022.07.
     >
     > To exit type 'exit' or '^D'
     > [0] > #beginning
     > Nil
     > [1] > my Str $y="xxxxxx"; S/^ x ** 2 /QQ/.say given $y;
     > QQxxxx
     > [1] > #inner
     > Nil
     > [2] > my Str $y="xxxxxx"; S/^ [x ** 2] <(x ** 2)> /QQ/.say given $y;
     > xxQQxx
     > [2] > #end
     > Nil
     > [3] > my Str $y="xxxxxx"; S/ x ** 2 $/QQ/.say given $y;
     > xxxxQQ
     >
     > HTH, Bill.
     >

    Yes it does!  Thank you!

    What does capitol S do?

Quote:

|S///| uses the same semantics as the |s///| operator, except it leaves the original string intact and /returns the resultant string/ instead of |$/| (|$/| still being set to the same values as with |s///|).

https://docs.raku.org/syntax/S$SOLIDUS$SOLIDUS$SOLIDUS <https://docs.raku.org/syntax/S$SOLIDUS$SOLIDUS$SOLIDUS>

And they give an example:

say S/o .+ d/new/ with 'old string';      # OUTPUT: «new string»

S:g/« (.)/$0.uc()/.say for <foo bar ber>; # OUTPUT: «Foo␤Bar␤Ber»

Which brings me back to the other of my criticisms
of the documentation.  The examples are high level
users showing off their skills making for a totally
useless example for beginners.  They should show a
simple example and then work up to the show off stuff.