Class: RPrec::Prec

Inherits:
Object
  • Object
show all
Defined in:
lib/rprec/prec.rb

Overview

Prec is an operator precedence.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(name, succs, ops) ⇒ Prec

Returns a new instance of Prec.

Parameters:

  • name (Symbol)
  • succs (Array<Symbol>)
  • ops (Array<Op>) 


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# File 'lib/rprec/prec.rb', line 9

def initialize(name, succs, ops)
  @name = name
  @succs = succs
  @ops = ops
end

Instance Attribute Details

#name ⇒ Symbol (readonly)

Returns:

  • (Symbol) 


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# File 'lib/rprec/prec.rb', line 18

def name
  @name
end

#ops ⇒ Array<RPrec::Op> (readonly)

Returns:



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# File 'lib/rprec/prec.rb', line 22

def ops
  @ops
end

#postfix_table ⇒ Hash{String => RPrec::Op} (readonly)

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Returns:



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# File 'lib/rprec/prec.rb', line 29

def postfix_table
  @postfix_table
end

#prefix_table ⇒ Hash{String => RPrec::Op} (readonly)

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Returns:



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# File 'lib/rprec/prec.rb', line 26

def prefix_table
  @prefix_table
end

#succs ⇒ Array<Symbol> (readonly)

Returns:

  • (Array<Symbol>) 


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# File 'lib/rprec/prec.rb', line 20

def succs
  @succs
end

Instance Method Details

#inspect ⇒ String

Returns:

  • (String) 


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# File 'lib/rprec/prec.rb', line 202

def inspect
  result = "prec #{name.inspect}"
  result << " => #{succs.inspect}" unless succs.empty?
  unless ops.empty?
    result << " do\n"
    ops.each do |op|
      result << "  #{op.inspect}\n"
    end
    result << 'end'
  end
  result
end

#parse(grammar, stream) ⇒ Object?

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Parameters:

Returns:

  • (Object, nil) 


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# File 'lib/rprec/prec.rb', line 71

def parse(grammar, stream)
  op = @prefix_table[stream.current.type]

  if op
    key_token = stream.current
    stream.next

    case op.type
    when :prefix
      parts = grammar.parse_parts(op.parts, stream)
      return parse_prefix_and_right_assoc(grammar, stream, [[op, [key_token, *parts]]])

    when :non_assoc_prefix
      parts = grammar.parse_parts(op.parts, stream)
      node = grammar.parse_precs(@succs, stream)
      return op.build(key_token, *parts, node)

    when :closed
      parts = grammar.parse_parts(op.parts, stream)
      return op.build(key_token, *parts)

    else raise ScriptError, 'Unreachable'
    end
  end
  stream.expected(@all_prefix_keys)

  node = grammar.parse_precs(@succs, stream)
  key_token = stream.current
  op = @postfix_table[key_token.type]
  unless op
    stream.expected(@all_postfix_keys)
    return node
  end
  stream.next

  case op.type
  when :postfix
    parts = grammar.parse_parts(op.parts, stream)
    node = op.build(node, key_token, *parts)
    parse_postfix_and_left_assoc(grammar, stream, node)

  when :non_assoc_postfix
    parts = grammar.parse_parts(op.parts, stream)
    op.build(node, key_token, *parts)

  when :left_assoc
    parts = grammar.parse_parts(op.parts, stream)
    right = grammar.parse_precs(@succs, stream)
    node = op.build(node, key_token, *parts, right)
    parse_postfix_and_left_assoc(grammar, stream, node)

  when :right_assoc
    parts = grammar.parse_parts(op.parts, stream)
    parse_prefix_and_right_assoc(grammar, stream, [[op, [node, key_token, *parts]]])

  when :non_assoc
    parts = grammar.parse_parts(op.parts, stream)
    right = grammar.parse_precs(@succs, stream)
    op.build(node, key_token, *parts, right)

  else raise ScriptError, 'Unreachable'
  end
end

#setup(grammar) ⇒ void

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

This method returns an undefined value.

Parameters:



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# File 'lib/rprec/prec.rb', line 34

def setup(grammar)
  return unless @prefix_table.nil? && @postfix_table.nil?

  @prefix_table = {}
  @postfix_table = {}

  @ops.each do |op|
    case op.type
    when :prefix, :non_assoc_prefix, :closed
      raise ArgumentError, "Conflict with the key token '#{op.key}'" if @prefix_table.include?(op.key)

      @prefix_table[op.key] = op
    when :postfix, :non_assoc_postfix, :left_assoc, :right_assoc, :non_assoc
      raise ArgumentError, "Conflict with the key token '#{op.key}'" if @postfix_table.include?(op.key)

      @postfix_table[op.key] = op
    end
  end

  grammar.setup(@succs)

  @ops.each do |op|
    parts = op.parts.filter_map { _1.is_a?(Symbol) ? _1 : nil }
    grammar.setup(parts)
  end

  @all_prefix_keys = @prefix_table.keys
  @all_postfix_keys = @postfix_table.keys
  @prefix_keys = @prefix_table.filter { |_, op| op.type == :prefix }.keys
  @right_assoc_keys = @postfix_table.filter { |_, op| op.type == :right_assoc }.keys
  @postfix_and_left_assoc_keys = @postfix_table.filter { |_, op| op.type == :postfix || op.type == :left_assoc }.keys
end