Re: Exception Handling, DivideByZero

2018-10-29 Thread Brad Gilbert
.WHAT gives you the actual type, whereas .^name gives you a string
that is the name.

In Perl6 types are things you can pass around; which is good because
you can have more than one with the same name.

sub bar (){
  my class Foo {  }
}
sub baz (){
  my class Foo {  }
}

my $a = bar().new();

bar() === $a.^name; # False (one is a Foo type object, the other a string)
bar() === $a.WHAT; # True (both are the Foo type object)

bar().^name === baz().^name; # True (but they are different types)
bar().WHAT === baz().WHAT; # False (both are type objects, but
they are different types)

"".WHAT =:= Str; # True (both are the Str type object)

Basically think about .WHAT as being the Perl6 equivalent of `typeof()`.
On Mon, Oct 29, 2018 at 12:12 PM Joseph Brenner  wrote:
>
> Brandon Allbery  wrote:
> > Two issues:
> >
> > (1) all standard exceptions are in or under the X:: namespace.
> >
> > (2) .WHAT doesn't show names with their namespaces, whereas .^name does.
> >
> > pyanfar Z$ 6 'my $r = 4/0; say $r; CATCH {default {say .^name}}'
> > X::Numeric::DivideByZero
>
> Thanks.  I didn't get that the behavior of WHAT and ^name were that different.
>
>
>
> > On Mon, Oct 29, 2018 at 1:04 PM Joseph Brenner  wrote:
> >
> >> I was just looking into doing some finer-grained exception handling,
> >> so I tried this:
> >>
> >>use v6;
> >>try {
> >>my $result = 4/0;
> >>say "result: $result";
> >>CATCH {
> >>#when DivideByZero { say "Oh, you know."; }
> >>default { say .WHAT; .Str.say } # (DivideByZero)   Attempt
> >> to divide 4 by zero using div
> >>}
> >>}
> >>
> >> The first time through, The .WHAT tells me I've got
> >> "DivideByZero", and so I added the line that's commented out
> >> here, at which point I got the error:
> >>
> >>===SORRY!===
> >>Function 'DivideByZero' needs parens to avoid gobbling block (or
> >> perhaps it's a class that's not declared or available in this scope?)
> >>
> >> Putting parens around (DivideByZero) doesn't help:
> >>
> >>Undeclared name:
> >>   DivideByZero used at line 12
> >>
> >> My impression was this would just work from looking
> >> at the examples using things like X::AdHoc here:
> >>
> >>   https://docs.perl6.org/language/exceptions
> >>
> >
> >
> > --
> > brandon s allbery kf8nh
> > allber...@gmail.com
> >


Re: Exception Handling, DivideByZero

2018-10-29 Thread Joseph Brenner
Brandon Allbery  wrote:
> Two issues:
>
> (1) all standard exceptions are in or under the X:: namespace.
>
> (2) .WHAT doesn't show names with their namespaces, whereas .^name does.
>
> pyanfar Z$ 6 'my $r = 4/0; say $r; CATCH {default {say .^name}}'
> X::Numeric::DivideByZero

Thanks.  I didn't get that the behavior of WHAT and ^name were that different.



> On Mon, Oct 29, 2018 at 1:04 PM Joseph Brenner  wrote:
>
>> I was just looking into doing some finer-grained exception handling,
>> so I tried this:
>>
>>use v6;
>>try {
>>my $result = 4/0;
>>say "result: $result";
>>CATCH {
>>#when DivideByZero { say "Oh, you know."; }
>>default { say .WHAT; .Str.say } # (DivideByZero)   Attempt
>> to divide 4 by zero using div
>>}
>>}
>>
>> The first time through, The .WHAT tells me I've got
>> "DivideByZero", and so I added the line that's commented out
>> here, at which point I got the error:
>>
>>===SORRY!===
>>Function 'DivideByZero' needs parens to avoid gobbling block (or
>> perhaps it's a class that's not declared or available in this scope?)
>>
>> Putting parens around (DivideByZero) doesn't help:
>>
>>Undeclared name:
>>   DivideByZero used at line 12
>>
>> My impression was this would just work from looking
>> at the examples using things like X::AdHoc here:
>>
>>   https://docs.perl6.org/language/exceptions
>>
>
>
> --
> brandon s allbery kf8nh
> allber...@gmail.com
>


Re: Exception Handling, DivideByZero

2018-10-29 Thread Brandon Allbery
Two issues:

(1) all standard exceptions are in or under the X:: namespace.

(2) .WHAT doesn't show names with their namespaces, whereas .^name does.

pyanfar Z$ 6 'my $r = 4/0; say $r; CATCH {default {say .^name}}'
X::Numeric::DivideByZero


On Mon, Oct 29, 2018 at 1:04 PM Joseph Brenner  wrote:

> I was just looking into doing some finer-grained exception handling,
> so I tried this:
>
>use v6;
>try {
>my $result = 4/0;
>say "result: $result";
>CATCH {
>#when DivideByZero { say "Oh, you know."; }
>default { say .WHAT; .Str.say } # (DivideByZero)   Attempt
> to divide 4 by zero using div
>}
>}
>
> The first time through, The .WHAT tells me I've got
> "DivideByZero", and so I added the line that's commented out
> here, at which point I got the error:
>
>===SORRY!===
>Function 'DivideByZero' needs parens to avoid gobbling block (or
> perhaps it's a class that's not declared or available in this scope?)
>
> Putting parens around (DivideByZero) doesn't help:
>
>Undeclared name:
>   DivideByZero used at line 12
>
> My impression was this would just work from looking
> at the examples using things like X::AdHoc here:
>
>   https://docs.perl6.org/language/exceptions
>


-- 
brandon s allbery kf8nh
allber...@gmail.com