Class: Rley::Syntax::Production

Inherits:
Object
  • Object
show all
Defined in:
lib/rley/syntax/production.rb

Overview

In a context-free grammar, a production is a rule in which its left-hand side (LHS) consists solely of a non-terminal symbol and the right-hand side (RHS) consists of a sequence of symbols. The symbols in RHS can be either terminal or non-terminal symbols. The rule stipulates that the LHS is equivalent to the RHS, in other words every occurrence of the LHS can be substituted to corresponding RHS.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(aNonTerminal, theSymbols) ⇒ Production

Returns a new instance of Production.



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# File 'lib/rley/syntax/production.rb', line 24

def initialize(aNonTerminal, theSymbols)
  @lhs = valid_lhs(aNonTerminal)
  @rhs = SymbolSeq.new(theSymbols)
end

Instance Attribute Details

#lhs ⇒ Object (readonly) Also known as: head

The left-hand side of the rule. It must be a non-terminal symbol



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# File 'lib/rley/syntax/production.rb', line 17

def lhs
  @lhs
end

#rhs ⇒ Object (readonly) Also known as: body

The right-hand side (rhs) consists of a sequence of grammar symbols



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# File 'lib/rley/syntax/production.rb', line 14

def rhs
  @rhs
end

Instance Method Details

#empty? ⇒ Boolean

Is the rhs empty? @ return true if the rhs has no members.

Returns:

  • (Boolean) 


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# File 'lib/rley/syntax/production.rb', line 31

def empty?()
  return rhs.empty?
end