On 09/11/2018 03:14 AM, Timo Paulssen wrote:
The colon at the end of "Str:D:" signifies that it's a type constraint
on what you call the method on. For example:
my Str $foo;
$foo.contains("hello", 0);
won't work because $foo is currently not defined, i.e. doesn't pass the
:D constraint. The : at the end means that the constraint "Str:D"
applies to what's before the method call, in this case $foo.
In this signature, the needle is not optional, and it doesn't make sense
to me to have it optional. What would it mean to ask if a string
contains, but not what it's supposed to contain?
Without having to look at the docs, I would expect $pos to mean the
position in the string that should be checked for presence of the needle
(as in: find a needle in a haystack).
The return value isn't shown in this definition, but I'd say that's an
oversight that should be fixed.
I hope that helps!
- Timo
On 11/09/18 12:09, ToddAndMargo wrote:
multi method contains(Str:D: Cool:D $needle, Int(Cool:D) $pos)
Okay, I know that
Str is a string
Cool is an object that can be treated as both a string and a number
$needle is the second optional parameter
What is "D"?
$needle is optional, why is it not stated as "$needle?"
How is both Str:D: and Cool:D the first parameter?
Why does "Str:D:" have a colon on the end and "Cool:D" does not?
What is Int(Cool:D) ?
What is $pos ?
Where is it stated that it has a return a value?
Where is it state that the return value is a boolean?
Yours in confusion,
-T
A little bit. Thank you! I will have to read it over several times.
Thank you.
As I understand it $needle? is the second optional parameter
and it is an integer, not "Cool" (both a string and a number).
I presume "Cool" includes real numbers too.
I have no idea how they got from
multi method contains(Str:D: Cool:D $needle, Int(Cool:D) $pos)
to
$ p6 'say "abc".contains("b");'
True
Perl 6's function reference has got to be the hardest
to understand I have ever come across. Perl 5's
"perldocs -v" were a bazillion times easier to understand.
-T
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