Class: Rley::Parser::ParseTracer

Inherits:
Object
  • Object
show all
Defined in:
lib/rley/parser/parse_tracer.rb

Overview

Utility class used to trace the parsing of a token sequence.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(aTraceLevel, anIO, aTokenSequence) ⇒ ParseTracer

Returns a new instance of ParseTracer.



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# File 'lib/rley/parser/parse_tracer.rb', line 17

def initialize(aTraceLevel, anIO, aTokenSequence)
  @level = aTraceLevel <= 0 ? 0 : [aTraceLevel, 2].min
  @ostream = anIO
  @lexemes = aTokenSequence.map(&:lexeme)

  emit_tokens
  emit_heading
end

Instance Attribute Details

#col_width ⇒ Object (readonly)

Returns the value of attribute col_width.



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# File 'lib/rley/parser/parse_tracer.rb', line 15

def col_width
  @col_width
end

#level ⇒ Object (readonly)

The trace level



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# File 'lib/rley/parser/parse_tracer.rb', line 13

def level
  @level
end

#lexemes ⇒ Object (readonly)

Returns the value of attribute lexemes.



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# File 'lib/rley/parser/parse_tracer.rb', line 14

def lexemes
  @lexemes
end

#ostream ⇒ Object (readonly)

The stream where the trace output is sent



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# File 'lib/rley/parser/parse_tracer.rb', line 10

def ostream
  @ostream
end

Instance Method Details

Emit the trace text to the output IO if the given trace level is equal or greater to the trace level of the tracer instance.



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# File 'lib/rley/parser/parse_tracer.rb', line 29

def print_if(aLevel, text)
  ostream.print(text) if level >= aLevel
end

#trace_completion(aStatesetIndex, aParseState) ⇒ Object 



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# File 'lib/rley/parser/parse_tracer.rb', line 49

def trace_completion(aStatesetIndex, aParseState)
  return unless level

  if aStatesetIndex == lexemes.size && aParseState.origin.zero? &&
     aParseState.complete?
    picture = '=' * (col_width * lexemes.size - 1)
  else
    count = col_width * (aStatesetIndex - aParseState.origin) - 1
    picture = '-' * count
  end
  completion_picture = "[#{picture}#{aParseState.complete? ? ']' : '>'}"
  trace_diagram(aStatesetIndex, aParseState, completion_picture)
end

#trace_prediction(aStatesetIndex, aParseState) ⇒ Object 



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# File 'lib/rley/parser/parse_tracer.rb', line 43

def trace_prediction(aStatesetIndex, aParseState)
  return unless level

  trace_diagram(aStatesetIndex, aParseState, '>')
end

#trace_scanning(aStatesetIndex, aParseState) ⇒ Object

Emit the trace of a scanning step.



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# File 'lib/rley/parser/parse_tracer.rb', line 34

def trace_scanning(aStatesetIndex, aParseState)
  return unless level

  scan_picture = "[#{'-' * (col_width - 1)}]"
  org = OpenStruct.new(origin: aStatesetIndex - 1,
                       dotted_rule: aParseState.dotted_rule)
  trace_diagram(aStatesetIndex, org, scan_picture)
end