Class: Eqn::Expression

Inherits:
Treetop::Runtime::SyntaxNode
  • Object
show all
Defined in:
lib/eqn/expression.rb

Defined Under Namespace

Classes: ExprGroup

Instance Method Summary collapse

Instance Method Details

#left_associative? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/eqn/expression.rb', line 3

def left_associative?
  elements.any? && elements.last.left_associative?
end

#term? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/eqn/expression.rb', line 7

def term?
  elements.empty?
end

#value ⇒ Object 



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# File 'lib/eqn/expression.rb', line 11

def value
  if elements.count == 1
    elements.shift.value
  else
    base = elements.shift.value

    # Aggressively consume left associative operators to maintain associativity.
    while left_associative?
      op, num_expr = elements.shift.value
      num_expr_operand = num_expr.elements.shift
      base = base.send(op, num_expr_operand.value)
      elements.push num_expr.elements.shift unless num_expr.term?
    end

    # Apply next right-associative operator (if any) or return.
    if term?
      base
    else
      op, num_expr = elements.shift.value
      base.send(op, num_expr.value)
    end
  end
end