Class: Multimethod::Multimethod

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

Overview

Represents a Multimethod.

A Multimethod has multiple implementations of a method based on the relative scoring of the argument types of the message.

A Multimethod has a name.

Constant Summary collapse

@@name_map =

Support

{
  '@' => 'AT',
  '=' => 'EQ',
  '<' => 'LT',
  '>' => 'GT',
  '+' => 'ADD',
  '-' => 'SUB',
  '*' => 'MUL',
  '/' => 'DIV',
  '%' => 'MOD',
  '^' => 'XOR',
  '|' => 'OR',
  '&' => 'AND',
  '!' => 'NOT',
  '~' => 'TIL',
  '_' => '',    # escape '_' as '_'
  nil => nil
}
@@name_rx = 
Regexp.new('(' + @@name_map.keys.collect{|x| Regexp.quote(x)}.join('|') + ')')

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(name, *opts) ⇒ Multimethod

Initialize a new Multimethod.

Raises:

  • (NameError) 


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# File 'lib/multimethod/multimethod.rb', line 24

def initialize(name, *opts)
  raise NameError, "multimethod name not specified" unless name && name.to_s.size > 0
  @debug = nil

  @name = name
  @name_i = 0
  @method = [ ]
  @dispatch = { }

  @lookup_method = { }
  
end

Instance Attribute Details

#debug ⇒ Object

Enable debugging info.



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# File 'lib/multimethod/multimethod.rb', line 21

def debug
  @debug
end

#method ⇒ Object

A list of Method’s that implement this Multimethod.



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# File 'lib/multimethod/multimethod.rb', line 15

def method
  @method
end

#name ⇒ Object

The Multimethod’s name.



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# File 'lib/multimethod/multimethod.rb', line 12

def name
  @name
end

#table ⇒ Object

The Multimethod::Table that owns this Multimethod.



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# File 'lib/multimethod/multimethod.rb', line 18

def table
  @table
end

Class Method Details

.normalize_name(name) ⇒ Object 



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# File 'lib/multimethod/multimethod.rb', line 261

def self.normalize_name(name)
  name = name.to_s.clone
  name.gsub!(@@name_rx){|x| "_#{@@name_map[x] || '_'}_"}

  name.intern
end

Instance Method Details

#add_method(method) ⇒ Object

Adds the new Method object to this Multimethod.



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# File 'lib/multimethod/multimethod.rb', line 62

def add_method(method)
  # THREAD CRITICAL BEGIN
  remove_method(method.signature)
  @method.push(method)
  method.multimethod = self
  @lookup_method = { } # flush cache
  # THREAD CRITICAL END
end

#ambiguous_methods(scores) ⇒ Object 



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# File 'lib/multimethod/multimethod.rb', line 172

def ambiguous_methods(scores)
  # Check for additional methods with the same score as
  # the first method.
  scores = scores.select{|x| x[0] == scores[0][0]}

  # Map to a list of signatures.
  scores.size > 1 ? scores.collect{|x| x[1].signature} : nil
end

#apply_method(meth, rcvr, args) ⇒ Object

Interface to Multimethod::Table

Raises:

  • (NameError) 


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

def apply_method(meth, rcvr, args)
  unless meth # && false
    $stderr.puts "Available multimethods for #{rcvr.class.name}##{@name}(#{args}):"
    $stderr.puts "  " + @method.sort{|a,b| a.min_args <=> b.min_args }.collect{|x| x.to_s(name)}.join("\n  ")
    $stderr.puts "\n"
  end
  raise NameError, "Cannot find multimethod for #{rcvr.class.name}##{@name}(#{args})" unless meth
  rcvr.send(meth.impl_name, *args)
end

#dispatch(rcvr, args) ⇒ Object 



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# File 'lib/multimethod/multimethod.rb', line 109

def dispatch(rcvr, args)
  apply_method(lookup_method(rcvr, args), rcvr, args)
end

#find_method(signature) ⇒ Object

Returns a list of all Methods that match the Signature.



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# File 'lib/multimethod/multimethod.rb', line 79

def find_method(signature)
  m = @method.select{|x| x.matches_signature(signature)}

  m
end

#gensym(name = nil) ⇒ Object

Generates a unique symbol for a method name. Method implementations will use a unique name for the implementation method. For example, for a Multimethod named “foo”, the Method name might be “_multimethod_12_foo”.



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# File 'lib/multimethod/multimethod.rb', line 41

def gensym(name = nil)
  name ||= @name
  "_multimethod_#{@name_i = @name_i + 1}_#{name}"
end

#install_dispatch(mod) ⇒ Object

Installs a dispatching method in the Module. This method will dispatch to the Multimethod for Method lookup and application.



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# File 'lib/multimethod/multimethod.rb', line 207

def install_dispatch(mod)
  # THREAD CRITICAL BEGIN
  unless @dispatch[mod]
    @dispatch[mod] = true
    # $stderr.puts "install_dispatch(#{name}) into #{mod}\n";
    mod.class_eval(body = <<-"end_eval", __FILE__, __LINE__)
def #{name}(*args)
  ::#{table.class.name}.instance.dispatch(#{name.inspect}, self, args)
end
end_eval
# $stderr.puts "install_dispatch = #{body}"
  end
  # THREAD CRITICAL END
end

#lookup_method(rcvr, args) ⇒ Object 



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# File 'lib/multimethod/multimethod.rb', line 126

def lookup_method(rcvr, args)
  args = args.clone
  args.unshift(rcvr)
  lookup_method_cached_(args)
end

#lookup_method_(args) ⇒ Object 



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# File 'lib/multimethod/multimethod.rb', line 147

def lookup_method_(args)
  scores = score_methods(@method, args)
  if scores.empty?
    # Method not found.
    result = nil
  else
    # Check for ambiguous methods.
    if result = ambiguous_methods(scores)
      raise NameError, "Ambiguous methods for multimethod '#{@name}' for (#{args.collect{|x| x.name}.join(', ')}): #{result.collect{|x| x.to_s}.join(', ')}"
    end

    # Select best scoring method.
    result = scores[0][1]
  end

  #if @name.to_s == 'bar'
  #  $stderr.puts "args = " + args.collect{|x| x.class.name + ' ' + x.to_s}.join(",  ")
  #  $stderr.puts "scores:\n  " + scores.collect{|x| x.inspect}.join("\n  ")
  # end


  result
end

#lookup_method_cached_(args) ⇒ Object 



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# File 'lib/multimethod/multimethod.rb', line 133

def lookup_method_cached_(args)
  args_type = args.collect{|x| x.class}

  # THREAD CRITICAL BEGIN
  unless result = @lookup_method[args_type]
    result = @lookup_method[args_type] =
      lookup_method_(args_type)
  end
  # THREAD CRITICAL END

  result
end

#matches_signature(signature) ⇒ Object

Returns true if this Multimethod matches the Signature.



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# File 'lib/multimethod/multimethod.rb', line 73

def matches_signature(signature)
  @name == signature.name
end

#new_method(mod, name, *args) ⇒ Object

Creates a new Method object bound to mod by name.



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# File 'lib/multimethod/multimethod.rb', line 47

def new_method(mod, name, *args)
  m = Method.new(gensym(name), mod, name, *args)
  add_method(m)
  m
end

#new_method_from_signature(signature) ⇒ Object

Create a new Method object using the Signature.



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# File 'lib/multimethod/multimethod.rb', line 54

def new_method_from_signature(signature)
  m = Method.new(gensym(name), signature)
  add_method(m)
  m
end

#remove_dispatch(mod) ⇒ Object

Removes the dispatching method in the Module.



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# File 'lib/multimethod/multimethod.rb', line 224

def remove_dispatch(mod)
  # THREAD CRITICAL BEGIN
  if @dispatch[mod]
    @dispatch[mod] = false
    # $stderr.puts "Removing dispatch for #{mod.name}##{name}"
    mod.class_eval("remove_method #{name.inspect}")
  end
  # THREAD CRITICAL END
end

#remove_method(x) ⇒ Object

Removes the method.



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# File 'lib/multimethod/multimethod.rb', line 86

def remove_method(x)
  case x
  when Signature
    m = find_method(x) 
    m = m[0]
    return unless m
    raise("No method found for #{x.to_s}") unless m
  else
    m = x
  end

  m.remove_implementation
  m.multimethod = nil
  @method.delete(m)
  @lookup_method = { } # flush cache

  # Remove multimethod dispatch in the method's module?
  if @method.collect{|x| m.signature.mod = m.signature.mod}.empty?
    remove_dispatch(m.signature.mod)
  end
end

#score_methods(meths, args) ⇒ Object

Returns a sorted list of scores and Methods that match the argument types.



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# File 'lib/multimethod/multimethod.rb', line 184

def score_methods(meths, args)
  scores = meths.collect do |meth|
    score = meth.score_cached(args)
    if score 
      score = [ score, meth ]
    else
      score = nil
    end

    score
  end

  scores.compact!
  scores.sort!
  
  $stderr.puts %{  score_methods(#{args.inspect}) => \n#{scores.collect{|x| x.inspect}.join("\n")}} if @debug

  scores
end