Sha256: caac6eb85e4a0557f8ede93a65cbd891525e581318e02fde301babdf9ab8bae4
Contents?: true
Size: 886 Bytes
Versions: 5
Compression:
Stored size: 886 Bytes
Contents
module Alf
module Algebra
class Project
include Operator
include Relational
include Unary
signature do |s|
s.argument :attributes, AttrList, []
s.option :allbut, Boolean, false, 'Project all but specified attributes?'
end
def heading
@heading ||= operand.heading.project(attributes, allbut)
end
def keys
@keys ||= operand.keys.select{|k|
k.project(attributes, allbut) == k
}.if_empty{ Keys[ heading.to_attr_list ] }
end
def key_preserving?
keys.any?{|k| operand.keys.include?(k) }
end
def stay_attributes
allbut ? heading.to_attr_list : attributes
end
private
def _type_check(options)
no_unknown!(attributes - operand.attr_list)
end
end # class Project
end # module Algebra
end # module Alf
Version data entries
5 entries across 5 versions & 1 rubygems