Re: I need help testing for Nil
On 2020-05-26 16:29, Brad Gilbert wrote: There are various equality operators. ｢==｣ Tests for numeric equality ｢eq｣ Tests for string equality ｢===｣ Tests for value identity ｢=:=｣ Tests for pointer equality (Note that it looks a bit like ｢:=｣) ｢eqv｣ Tests for structure equivalence. The ｢==｣ and ｢eq｣ operators are special because they force their values to be numbers or strings before they do anything else. Thank you! Wrote it down.
Re: I need help testing for Nil
There are various equality operators.
｢==｣ Tests for numeric equality
｢eq｣ Tests for string equality
｢===｣ Tests for value identity
｢=:=｣ Tests for pointer equality (Note that it looks a bit like ｢:=｣)
｢eqv｣ Tests for structure equivalence.
The ｢==｣ and ｢eq｣ operators are special because they force their values to
be numbers or strings before they do anything else.
There are similarly a variety of comparison operators.
On Tue, May 26, 2020 at 5:06 PM ToddAndMargo via perl6-users <
perl6-users@perl.org> wrote:
> >> On Tue, May 26, 2020 at 4:24 PM ToddAndMargo via perl6-users
> >> mailto:perl6-users@perl.org>> wrote:
> >>
> >> Hi All,
> >>
> >> How do I turn this:
> >>
> >> $ raku -e 'my $x="abc"; say $x.index( "q" );'
> >> Nil
> >>
> >> into a test?
> >>
> >> $ raku -e 'my $x="abc"; if $x.index( "q" ) eq Nil {say
> "Nil"}else{say
> >> "Exists";}'
> >> Use of Nil in string context
> >> in block at -e line 1
> >> Use of Nil in string context
> >> in block at -e line 1
> >> Nil
> >>
> >>
> >> Many thanks,
> >> -T
> >>
>
> On 2020-05-26 15:00, Brad Gilbert wrote:
> > Generally you don't need to test for ｢Nil｣.
> > You can just test for defined-ness.
>
> True enough
>
> >
> > $ raku -e 'my $x="abc"; with $x.index( "q" ) {say "Exists"} else
> > {say "Nil";}'
> >
> > Also ｢Nil｣ is not a ｢Str｣, so why would you use ｢eq｣?
>
> Because == did not work
>
>
> > $ raku -e 'Nil.Str'
> > Use of Nil in string context
> >
> > If you really need to check specifically for ｢Nil｣ (which you probably
> > don't), then you can use ｢===｣.
> >
> > for Str, Int, Nil {
> > say 'Nil' if $_ === Nil;
> > }
> >
> > The ｢//｣ operator can also be useful to deal with undefined values such
> > as ｢Nil｣.
> >
> > my $x = 'abc';
> > say $x.index('q') // 'cannot find the index of ｢q｣';
> >
> >
>
> Hi Brad,
>
> Did not know about the triple =
>
> Thank you!
>
> -T
>
>
> $ raku -e 'my $x="abc"; if $x.index( "q" ) === Nil {say "Nil"}else{say
> "Exists";}'
> Nil
>
> $ raku -e 'my $x="abc"; if $x.index( "a" ) === Nil {say "Nil"}else{say
> "Exists";}'
> Exists
>
> And I found buried in my Nil notes that `=:=` works too
>
> $ raku -e 'my $x="abc"; if $x.index( "q" ) =:= Nil {say "Nil"}else{say
> "Exists";}'
> Nil
>
> $ raku -e 'my $x="abc"; if $x.index( "b" ) =:= Nil {say "Nil"}else{say
> "Exists";}'
> Exists
>
Re: I need help testing for Nil
On Tue, May 26, 2020 at 4:24 PM ToddAndMargo via perl6-users
mailto:perl6-users@perl.org>> wrote:
Hi All,
How do I turn this:
$ raku -e 'my $x="abc"; say $x.index( "q" );'
Nil
into a test?
$ raku -e 'my $x="abc"; if $x.index( "q" ) eq Nil {say "Nil"}else{say
"Exists";}'
Use of Nil in string context
in block at -e line 1
Use of Nil in string context
in block at -e line 1
Nil
Many thanks,
-T
On 2020-05-26 15:00, Brad Gilbert wrote:
Generally you don't need to test for ｢Nil｣.
You can just test for defined-ness.
True enough
$ raku -e 'my $x="abc"; with $x.index( "q" ) {say "Exists"} else
{say "Nil";}'
Also ｢Nil｣ is not a ｢Str｣, so why would you use ｢eq｣?
Because == did not work
$ raku -e 'Nil.Str'
Use of Nil in string context
If you really need to check specifically for ｢Nil｣ (which you probably
don't), then you can use ｢===｣.
for Str, Int, Nil {
say 'Nil' if $_ === Nil;
}
The ｢//｣ operator can also be useful to deal with undefined values such
as ｢Nil｣.
my $x = 'abc';
say $x.index('q') // 'cannot find the index of ｢q｣';
Hi Brad,
Did not know about the triple =
Thank you!
-T
$ raku -e 'my $x="abc"; if $x.index( "q" ) === Nil {say "Nil"}else{say
"Exists";}'
Nil
$ raku -e 'my $x="abc"; if $x.index( "a" ) === Nil {say "Nil"}else{say
"Exists";}'
Exists
And I found buried in my Nil notes that `=:=` works too
$ raku -e 'my $x="abc"; if $x.index( "q" ) =:= Nil {say "Nil"}else{say
"Exists";}'
Nil
$ raku -e 'my $x="abc"; if $x.index( "b" ) =:= Nil {say "Nil"}else{say
"Exists";}'
Exists
Re: I need help testing for Nil
Generally you don't need to test for ｢Nil｣.
You can just test for defined-ness.
$ raku -e 'my $x="abc"; with $x.index( "q" ) {say "Exists"} else {say
"Nil";}'
Also ｢Nil｣ is not a ｢Str｣, so why would you use ｢eq｣?
$ raku -e 'Nil.Str'
Use of Nil in string context
If you really need to check specifically for ｢Nil｣ (which you probably
don't), then you can use ｢===｣.
for Str, Int, Nil {
say 'Nil' if $_ === Nil;
}
The ｢//｣ operator can also be useful to deal with undefined values such as
｢Nil｣.
my $x = 'abc';
say $x.index('q') // 'cannot find the index of ｢q｣';
On Tue, May 26, 2020 at 4:24 PM ToddAndMargo via perl6-users <
perl6-users@perl.org> wrote:
> Hi All,
>
> How do I turn this:
>
> $ raku -e 'my $x="abc"; say $x.index( "q" );'
> Nil
>
> into a test?
>
> $ raku -e 'my $x="abc"; if $x.index( "q" ) eq Nil {say "Nil"}else{say
> "Exists";}'
> Use of Nil in string context
>in block at -e line 1
> Use of Nil in string context
>in block at -e line 1
> Nil
>
>
> Many thanks,
> -T
>
