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Things like this seem like odd design choices: my @menu = <hamburger fries milkshake>; say @menu.contains('hamburger'); # True say @menu.cont

Things like this seem like odd design choices: my @menu = <hamburger fries milkshake>; say @menu.contains('hamburger'); # True say @menu.contains('hot dog'); # False say @menu.contains('milk'); # True! say @menu.contains('er fr'); # True! say @menu.contains(<es mi>); # True!

raiph 8y ago
English contains ambiguous words. What does "contains" mean in the previous sentence? In P6 it means searching a string for a substring. Your code asks P6 to treat @menu as a string. If you want to treat it as a list and grep that list then use grep: my @menu = <hamburger fries milkshake>; say so @menu.grep('hamburger'); # True say so @menu.grep('hot dog'); # False say so @menu.grep('milk'); # False say so @menu.grep('er fr'); # False say so @menu.grep(<es mi>); # False
xisukar 8y ago
From https://docs.perl6.org/routine/contains https://docs.perl6.org/routine/contains, `contains` coerces its invocant to a string and searches for a substring starting from a certain position (index 0 by default): # Let's drop `<>` (quote-words constructor) and # use a more familiar array of strings: my @menu = 'hamburger', 'fries', 'milkshake'; # Let's look at the definition of the `Str` method in # the `List` class from which the `Array` class inherits: #`{ method Str(List:D: --> Str:D) Stringifies the elements of the list and joins them with spaces (same as .join(' ')). } # Thus, after being stringfied, @menu is treated as # the string 'hamburger fries milkshake' # With this is in hand, we can gauge the possible # result of the following statements: say @menu.contains('hamburger'); # True say @menu.contains('hot dog'); # False say @menu.contains('milk'); # True say @menu.contains('er fr'); # True say @menu.contains(<es mi>); # True If you'd like instead to search the array for words as elements, we could use Perl 6's set functions. However, I don't know if they're as performant as regular string searches: say 'hamburger' (<=) @menu; # True say 'fries' (<=) @menu; # True say 'hot dog' ∈ @menu; # False say 'milk' ∈ @menu; # False say 'er fr' ∈ @menu; # False `∈` is the unicode equivalent of `(<=)`. --- I'm not sure if I'm missing something in the "odd design choices" in this specific case so it'd be great if you could elaborate a little bit further here.
- lizmat 8y ago
  The ASCII equivalent of `∈` is `(elem)`.
  - xisukar 8y ago
    You're totally right! I always get them confused. So `∈` is `(elem)` and `⊆` is `(<=)`. Thanks for pointing it out!
b2gills 8y ago
You are sort-of right. It should have used a different word. A similar example would be the word `length`. There is no `length` in Perl 6 because it is ambiguous. Instead there is `.elems` and `.chars`. It is perhaps even a worse because there are other languages which use `contains` to see if the container has a given element.

raiph 8y ago

English contains ambiguous words. What does "contains" mean in the previous sentence? In P6 it means searching a string for a substring. Your code asks P6 to treat @menu as a string. If you want to treat it as a list and grep that list then use grep: my @menu = <hamburger fries milkshake>; say so @menu.grep('hamburger'); # True say so @menu.grep('hot dog'); # False say so @menu.grep('milk'); # False say so @menu.grep('er fr'); # False say so @menu.grep(<es mi>); # False

xisukar 8y ago

From https://docs.perl6.org/routine/contains https://docs.perl6.org/routine/contains, `contains` coerces its invocant to a string and searches for a substring starting from a certain position (index 0 by default): # Let's drop `<>` (quote-words constructor) and # use a more familiar array of strings: my @menu = 'hamburger', 'fries', 'milkshake'; # Let's look at the definition of the `Str` method in # the `List` class from which the `Array` class inherits: #`{ method Str(List:D: --> Str:D) Stringifies the elements of the list and joins them with spaces (same as .join(' ')). } # Thus, after being stringfied, @menu is treated as # the string 'hamburger fries milkshake' # With this is in hand, we can gauge the possible # result of the following statements: say @menu.contains('hamburger'); # True say @menu.contains('hot dog'); # False say @menu.contains('milk'); # True say @menu.contains('er fr'); # True say @menu.contains(<es mi>); # True If you'd like instead to search the array for words as elements, we could use Perl 6's set functions. However, I don't know if they're as performant as regular string searches: say 'hamburger' (<=) @menu; # True say 'fries' (<=) @menu; # True say 'hot dog' ∈ @menu; # False say 'milk' ∈ @menu; # False say 'er fr' ∈ @menu; # False `∈` is the unicode equivalent of `(<=)`. --- I'm not sure if I'm missing something in the "odd design choices" in this specific case so it'd be great if you could elaborate a little bit further here.

lizmat 8y ago
The ASCII equivalent of `∈` is `(elem)`.
- xisukar 8y ago
  You're totally right! I always get them confused. So `∈` is `(elem)` and `⊆` is `(<=)`. Thanks for pointing it out!

b2gills 8y ago

You are sort-of right. It should have used a different word. A similar example would be the word `length`. There is no `length` in Perl 6 because it is ambiguous. Instead there is `.elems` and `.chars`. It is perhaps even a worse because there are other languages which use `contains` to see if the container has a given element.