Method: Bmg::Type#transform

Defined in:

lib/bmg/type.rb

#transform(transformation, options = {}) ⇒ Object

# File 'lib/bmg/type.rb', line 244

def transform(transformation, options = {})
  transformer = TupleTransformer.new(transformation)
  if typechecked? && knows_attrlist? && transformer.knows_attrlist?
    known_attributes!(transformer.to_attrlist)
  end
  keys = if options[:key_preserving]
    self._keys
  elsif transformer.knows_attrlist? && knows_keys?
    touched_attrs = transformer.to_attrlist
    keys = self._keys.select{|k| (k & touched_attrs).empty? }
  else
    nil
  end
  pred = if transformer.knows_attrlist?
    attr_list = transformer.to_attrlist
    predicate.and_split(attr_list).last
  else
    Predicate.tautology
  end
  dup.tap{|x|
    x.keys = keys
    x.predicate = pred
  }
end