On Sun, Jun 07, 2020 at 09:04:45AM -0500, Brad Gilbert wrote:
> On Sun, Jun 7, 2020 at 3:15 AM ToddAndMargo via perl6-users <
> perl6-us...@perl.org> wrote:
>
> > Hi All,
> >
> > Dumb question:
> >
> > Does the "multi" in "multi method" mean there
> > is more than one way to address a method?
> >
> > Or, are the all methods "multi methods".
> >
> > If not and the method is a multi, should not the
> > documentation show all (more than one) the ways of
> > addressing a multi method?
>
> There are four different types of a function. (both method and sub)
>
> - `multi`
> - `proto`
> - `only`
> - `anon`
>
> A `proto` function is mainly just to declare there will be multiple
> functions with same name.
> `multi` is short for "multiple", meaning more than one.
> `only` is the default, it means there is only one.
> `anon` is for creating a lambda. (You only need it if you give the function
> a name.)
>
> Again this applies to both subs and methods.
> (Also `regex`, `token`, and `rule`. As they are just special methods.)
>
> only sub foo (){}
> only sub foo (1){} # ERROR: redeclaration
> # note that `only` is optional, as it is the default.
>
> proto sub bar (|){*}
> multi sub bar (){}
> multi sub bar (1){}
> # note that defining a `proto` function is optional
>
> my $var = anon sub baz (){ 'fuzz' };
> say baz(); # ERROR: can't find a sub named `baz`
> say $var(); # fuzz
> say $var.name; # baz
I believe, though I'm not sure, that Todd may be referring to one of
the questions that came up in a longish recent thread, namely the fact
that the documentation of Str.starts-with() seems to only document it as
a Str method, while Raku seems to disagree:
[roam@straylight ~]$ raku -e 'my Str $x; $x.starts-with("a")'
Cannot resolve caller starts-with(Str:U: Str:D); none of these signatures match:
(Cool:D: Cool:D $needle, :i(:$ignorecase)!, :m(:$ignoremark), *%_ --> Bool)
(Cool:D: Cool:D $needle, :m(:$ignoremark)!, *%_ --> Bool)
(Cool:D: Cool:D $needle, *%_ --> Bool)
(Str:D: Str:D $needle, :i(:$ignorecase)!, :m(:$ignoremark), *%_ --> Bool)
(Str:D: Str:D $needle, :m(:$ignoremark)!, *%_ --> Bool)
(Str:D: Str:D $needle, *%_ --> Bool)
in block <unit> at -e line 1
[roam@straylight ~]$
So it seems that Cool has a .starts-with() method too, and this is borne
out by a further experiment:
[roam@straylight ~]$ raku -e 'my Cool $x; $x.starts-with("a")'
Cannot resolve caller starts-with(Cool:U: Str:D); none of these signatures
match:
(Cool:D: Cool:D $needle, :i(:$ignorecase)!, :m(:$ignoremark), *%_ --> Bool)
(Cool:D: Cool:D $needle, :m(:$ignoremark)!, *%_ --> Bool)
(Cool:D: Cool:D $needle, *%_ --> Bool)
in block <unit> at -e line 1
[roam@straylight ~]$
So the truth is that I do not fully understand why the documentation
does not list .starts-with() as a method for Cool as well as Str: in
https://docs.raku.org/routine.html "starts-with" is listed as "from
Str", while there are other methods that are listed as "from Cool, Str",
e.g. "subst".
Now, yeah, I understand that Str.starts-with() defines a coercion for
its $needle argument that means that Cool.starts-with() will never be
called for an invocant that is either a Str or of any type derived from
Str, no matter what $needle is - if it is from another Cool-derived
type, it will be coerced to Str and Str.starts-with() will be called.
However, should the documentation not mention that another type derived
from Cool will also have a .starts-with() method?
Please note that I'm not criticizing the documentation, automatically
generated or not, or the efforts of everyone involved in producing it :)
I am under the impression that it is, at least to some extent,
automatically generated, so I'm genuinely curious what is it about
the .starts-with() method that has caused it to lose its Cool :)
...and, of course, it may turn out that Todd meant something completely
different in this particular message and I hijacked the thread...
G'luck,
Peter
--
Peter Pentchev r...@ringlet.net r...@debian.org p...@storpool.com
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