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extend Algebrick::Matching # => main
def deliver_email(email)
true
end
Contact = Algebrick.type do |contact|
variants Null = atom,
contact
fields username: String, email: String
end
# => Contact(Null | Contact(username: String, email: String))
module Contact
def username
match self,
Null >> 'no name',
Contact >-> { self[:username] }
end
def email
match self,
Null >> 'no email',
Contact >-> { self[:email] }
end
def deliver_personalized_email
match self,
Null >> true,
Contact >-> { deliver_email(self.email) }
end
end
peter = Contact['peter', 'example@dot.com'] # => Contact[username: peter, email: example@dot.com]
john = Contact[username: 'peter', email: 'example@dot.com']
# => Contact[username: peter, email: example@dot.com]
nobody = Null # => Null
[peter, john, nobody].map &:email
# => ["example@dot.com", "example@dot.com", "no email"]
[peter, john, nobody].map &:deliver_personalized_email
# => [true, true, true]
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