Class: GhostWheel::Expression::LookAhead

Inherits:
GhostWheel::Expression show all
Defined in:
lib/ghost_wheel/expression/look_ahead.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods inherited from GhostWheel::Expression

#parse

Constructor Details

#initialize(expression, negate = false) ⇒ LookAhead

Returns a new instance of LookAhead.



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# File 'lib/ghost_wheel/expression/look_ahead.rb', line 6

def initialize(expression, negate = false)
  @expression = expression
  @negate     = negate
end

Instance Attribute Details

#expression ⇒ Object (readonly)

Returns the value of attribute expression.



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# File 'lib/ghost_wheel/expression/look_ahead.rb', line 11

def expression
  @expression
end

#negate ⇒ Object (readonly) Also known as: negate?

Returns the value of attribute negate.



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# File 'lib/ghost_wheel/expression/look_ahead.rb', line 11

def negate
  @negate
end

Instance Method Details

#==(other) ⇒ Object 



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# File 'lib/ghost_wheel/expression/look_ahead.rb', line 28

def ==(other)
  super and @expression == other.expression and @negate == other.negate
end

#uncached_parse(scanner, cache) ⇒ Object 



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# File 'lib/ghost_wheel/expression/look_ahead.rb', line 14

def uncached_parse(scanner, cache)
  matched = nil
  scanner.transaction do
    matched = @expression.parse(scanner, cache)
    scanner.abort
  end

  if matched.is_a? FailedParseResult
    @negate ? EmptyParseResult.instance : matched
  else
    @negate ? FailedParseResult.instance : EmptyParseResult.instance
  end
end