Module: LambdaDriver::Liftable

Included in:
Method, Proc, Symbol
Defined in:
lib/lambda_driver/liftable.rb

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.included(klass) ⇒ Object 



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# File 'lib/lambda_driver/liftable.rb', line 33

def self.included(klass)
  klass.send(:alias_method, :<=, :compose_with_lifting)
end

Instance Method Details

#>=(g) ⇒ Object 



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# File 'lib/lambda_driver/liftable.rb', line 29

def >=(g)
  g.to_proc <= self
end

#compose_with_lifting(g) ⇒ Object

compose self and give fuction with checking g(x) is mzero. if g(x) is mzero, it does not call self and return g(x), otherwise returns f(g(x)).

mzero means the object is nil or emtpy

hash = {:a => "foo"}
f = lambda{|y| y.length }
g = lambda{|y| hash[y]}
h = f.compose_with_lifting g
h.(:a) # => 3
h.(:b) # => nil (it does not called f)

This method is aliased as ‘<=`.

f <= g # => f.compose_with_lifting(g)



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# File 'lib/lambda_driver/liftable.rb', line 21

def compose_with_lifting(g)
  lambda{|*args|
    result = g.to_proc.call(*args)
    mzero_method = result.respond_to?(:mzero?) ? :mzero? : :nil?
    result.send(mzero_method) ? result : self.to_proc.call(result)
  }
end