Pretzel_map

What’s the pretzel map?
This is the pretzel (&).. and this is the pretzel map:

[1,2,3,4].map(&:to_s) # => ["1", "2", "3", "4"]

The object (Integer) in this case.. must have the method .to_s.

It’s like: [1,2,3,4].map {|i| i.to_s }

You can add a method to the object and call that:

class Integer
    def ior = 'åsna'
end

p [1,2,3].map(&:ior) # => ["åsna", "åsna", "åsna"]

But it’s not limited to object method calls…

ar = [*1..7]

def koko(x) = (x*2)

monkey = proc {it*2}
apa = :monkey


p ar.map(&method(:koko)) # method
p ar.map(&proc {it*2}) # proc
p ar.map(&monkey) # proc by var
p ar.map(&->{it*2}) # lambda
p ar.map(&eval(apa.to_s)) # proc by eval var

# 5 times => [2, 4, 6, 8, 10, 12, 14]