Class: OedipusLex::Rule

Inherits:
Struct
  • Object
show all
Defined in:
lib/oedipus_lex.rb

Overview

A Rule represents the main component of Oedipus Lex. These are the things that “get stuff done” at the lexical level. They consist of:

+ an optional required start state symbol or predicate method name + a regexp to match on + an optional action method or block

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(start_state, regexp, action) ⇒ Rule

:nodoc:



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# File 'lib/oedipus_lex.rb', line 115

def initialize start_state, regexp, action # :nodoc:
  super
  self.group = nil
end

Instance Attribute Details

#action ⇒ Object

Returns the value of attribute action

Returns:

  • (Object) —

    the current value of action



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# File 'lib/oedipus_lex.rb', line 100

def action
  @action
end

#group ⇒ Object Also known as: group?

What group this rule is in, if any.



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# File 'lib/oedipus_lex.rb', line 104

def group
  @group
end

#regexp ⇒ Object

Returns the value of attribute regexp

Returns:

  • (Object) —

    the current value of regexp



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# File 'lib/oedipus_lex.rb', line 100

def regexp
  @regexp
end

#start_state ⇒ Object

Returns the value of attribute start_state

Returns:

  • (Object) —

    the current value of start_state



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# File 'lib/oedipus_lex.rb', line 100

def start_state
  @start_state
end

Class Method Details

.[](start, regexp, action) ⇒ Object

A simple constructor



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# File 'lib/oedipus_lex.rb', line 111

def self.[] start, regexp, action
  new start, regexp.inspect, action
end

Instance Method Details

#pretty_print(pp) ⇒ Object

:nodoc:



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# File 'lib/oedipus_lex.rb', line 159

def pretty_print pp # :nodoc:
  pp.text "Rule"
  pp.group 2, "[", "]" do
    pp.pp start_state
    pp.text ", "
    pp.text regexp
    pp.text ", "
    pp.send(action ? :text : :pp, action)
  end
end

#to_ruby(state, predicates, exclusive) ⇒ Object

Generate equivalent ruby code for the rule.



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# File 'lib/oedipus_lex.rb', line 125

def to_ruby state, predicates, exclusive
  return unless group? or
    start_state == state or
    (state.nil? and predicates.include? start_state)

  uses_text = false

  body =
    case action
    when nil, false then
      "  # do nothing"
    when /^\{/ then
      uses_text = action =~ /\btext\b/
      "  action #{action}"
    when /^:/, "nil" then
      "  [:state, #{action}]"
    else # plain method name
      uses_text = true
      "  #{action} text"
    end

  check = uses_text ? "text = ss.scan(#{regexp})" : "ss.skip(#{regexp})"

  cond = if exclusive or not start_state then
           check
         elsif /^:/.match?(start_state) then
           "(state == #{start_state}) && (#{check})"
         else # predicate method
           "#{start_state} && (#{check})"
         end

  ["when #{cond} then", body]
end