Module: Rus3::EmptyList

Included in:
Error, Rus3::Evaluator::Environment, Pair, Procedure::Control, Procedure::List, Procedure::Predicate, Procedure::Vector, Procedure::Write
Defined in:
lib/rus3.rb

Overview

An empty list is a special object in Scheme language. The role roughly corresponds to the one of ‘nil’ in Ruby.

Constant Summary collapse

EMPTY_LIST =

Represents an empty list.

[]

Instance Method Summary collapse

Instance Method Details

#null?(obj) ⇒ Boolean

Returns true if the argument is an empty list. RuS^3 treats nil (an instance of NilClass) as an empty list.

Returns:

  • (Boolean) 


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# File 'lib/rus3.rb', line 19

def null?(obj)
  obj.instance_of?(Array) and obj.empty?
end