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Contents
# -*- encoding: utf-8 -*-
module SXP
##
class Pair
# @return [Object]
attr_accessor :head
# @return [Object]
attr_accessor :tail
##
# @param [Object] head
# @param [Object] tail
def initialize(head = nil, tail = nil)
@head, @tail = head, tail
end
##
# Returns `true` if the head and tail of this pair are both `nil`.
#
# @return [Boolean]
def empty?
head.nil? && tail.nil?
end
##
# Returns `true` if the tail of this pair is not `nil` or another pair.
#
# @return [Boolean]
# @see http://srfi.schemers.org/srfi-1/srfi-1.html#ImproperLists
def dotted?
!proper?
end
##
# Returns `true` if the tail of this pair is `nil` or another pair.
#
# @return [Boolean]
# @see http://srfi.schemers.org/srfi-1/srfi-1.html#ImproperLists
def proper?
tail.nil? || tail.is_a?(Pair)
end
##
# Returns an array representation of this pair.
#
# @return [Array]
def to_a
[head, tail]
end
##
# Returns a developer-friendly representation of this pair.
#
# @return [String]
def inspect
case
when tail.nil?
"(#{head.inspect})"
else
"(#{head.inspect} . #{tail.inspect})"
end
end
end # Pair
end # SXP
Version data entries
7 entries across 7 versions & 1 rubygems