On Tue, May 5, 2020 at 8:01 AM Gianni Ceccarelli <dak...@thenautilus.net> wrote:
>
> On 2020-05-05 William Michels via perl6-users <perl6-us...@perl.org>
> wrote:
> > mbook:~ homedir$ perl6 -ne 'put .chop' demo1.txt
> > this is a test
> > I love Unix
> > I like Linux too
> > mbook:~ homedir$ perl6 -pe '.chop' demo1.txt
> > this is a test,
> > I love Unix,
> > I like Linux too,
>
> The ``.chop`` method does not mutate its argument, it only returns a
> chopped value. If you want to mutate, you need to say so::
>
> raku -pe '.=chop' demo1.txt
>
> Notice that the ``.=`` operator is:
>
> * not specific to ``chop``
> * not even specific to calling methods
>
> In the same way that ``$a += 1`` is the same as ``$a = $a + 1``, so
> ``$a .= chop`` is the same as ``$a = $a.chop``.
>
> So, if you wanted, you could do::
>
> raku -pe '.=uc' # print upper-case
>
> --
I appreciate the reply, but your answer fails to explain one thing:
why does chop work without ".=" assignment using the "-ne" one-liner
flag, but not with the "-ne" one-liner flag"? According to the help
screen (running 'perl6 -help' at the bash command prompt), this is
what it says about the "-n" and the "-e" flags:
-n run program once for each line of input
-p same as -n, but also print $_ at the end of lines
So what strikes me from the definitions above is the part where "-p"
is the "same as -n... (with autoprinting of $_)." That leads people to
believe that they can write a short one-liner with the -ne flag ('put
.chop') and an even shorter one-liner with the -pe flag ('.chop').
If the only difference between the "-n" and "-p" flags is really that
the second one autoprints $_, I would have expected the "-pe" code
above to work identically to the "-ne" case (except "-ne" requires a
print, put or say). Presumably 'perl6 -ne "put .chop" ' is the same
as 'perl6 -ne ".chop.put" ' , so if ".put" isn't returning $_ ,
what is it returning then?
Look, It's no big deal if I have to write 'perl6 -pe ".=chop" '
instead of 'perl6 -pe ".chop" ', I just want to resolve in my mind a
perceived inconsistency wherein there's no requirement to write
'perl6 -ne "put .=chop" ' for the "-ne" case, but there IS a
requirement to write 'perl6 -pe ".=chop" ' for the "-pe" case.
Best Regards, Bill.
