Class: Rley::Lexical::TokenRange

Inherits:
Object
  • Object
show all
Defined in:
lib/rley/lexical/token_range.rb

Overview

A token range (also called an extent) represents an interval of token positions that is matched by a given grammar symbol. For instance consider the expression E: 3 + 11, let's assume that the integer literal '3' is the fifth input token and that the '+' and '11' tokens are respectively at position 6 and 7; then the token range associated with E is [5, 7] While the parse tree/forest is being constructed the boundaries of the token range can be temporarily undefined (= set to nil)

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(aRangeRep) ⇒ TokenRange

Constructor

Parameters:

  • aRangeRep (Hash) —

    A hash with keys :low and :high



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# File 'lib/rley/lexical/token_range.rb', line 24

def initialize(aRangeRep)
  assign_low(aRangeRep)
  assign_high(aRangeRep)
end

Instance Attribute Details

#high ⇒ Integer (readonly)

The index of the upper bound of token range

Returns:

  • (Integer) 


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# File 'lib/rley/lexical/token_range.rb', line 20

def high
  @high
end

#low ⇒ Integer (readonly)

The index of the lower bound of token range

Returns:

  • (Integer) 


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# File 'lib/rley/lexical/token_range.rb', line 16

def low
  @low
end

Instance Method Details

#==(other) ⇒ Boolean

Test for equality of ranges.

Parameters:

Returns:

  • (Boolean) 


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# File 'lib/rley/lexical/token_range.rb', line 32

def ==(other)
  return true if equal?(other)

  case other
    when Hash
      result = low == other[:low] && high == other[:high]
    when TokenRange
      result = low == other.low && high == other.high
    when Range
      result = low == other.first && high == other.last
    when Array
      result = low == other[0] && high == other[1]
  end

  return result
end

#assign(aRange) ⇒ Object

Conditional assign



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# File 'lib/rley/lexical/token_range.rb', line 55

def assign(aRange)
  return if bounded?

  assign_low(aRange) if low.nil?
  assign_high(aRange) if high.nil?
end

#bounded? ⇒ Boolean

true when both bounds aren't nil.

Returns:

  • (Boolean) 


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# File 'lib/rley/lexical/token_range.rb', line 50

def bounded?
  !(low.nil? || high.nil?)
end

#out_of_range?(index) ⇒ Boolean

Tell whether the given index value lies outside the range

Returns:

  • (Boolean) 


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# File 'lib/rley/lexical/token_range.rb', line 63

def out_of_range?(index)
  result = false
  result = true if !low.nil? && index < low
  result = true if !high.nil? && index > high

  return result
end

#to_string(_indentation) ⇒ Object

Emit a (formatted) string representation of the range. Mainly used for diagnosis/debugging purposes.



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# File 'lib/rley/lexical/token_range.rb', line 73

def to_string(_indentation)
  low_text = low.nil? ? '?' : low.to_s
  high_text = high.nil? ? '?' : high.to_s

  "[#{low_text}, #{high_text}]"
end