From: "rosenfeld (Rodrigo Rosenfeld Rosas)" <rr.rosas@...>
Date: 2012-07-09T22:26:45+09:00
Subject: [ruby-core:46269] [ruby-trunk - Feature #6711] Optional typing and method overloading


Issue #6711 has been updated by rosenfeld (Rodrigo Rosenfeld Rosas).


Actually the precedence should be:

1 - max number of matched argument types
2 - max number of better matched argument types # Float is a better match for 1.2 than Numeric
3 - max number of consecutive matched argument types
----------------------------------------
Feature #6711: Optional typing and method overloading
https://bugs.ruby-lang.org/issues/6711#change-27891

Author: rosenfeld (Rodrigo Rosenfeld Rosas)
Status: Open
Priority: Normal
Assignee: matz (Yukihiro Matsumoto)
Category: core
Target version: 3.0


Today I woke up with some ideas to overcome some of the features I miss in Ruby. I've searched for similar issues and I found this #5583, which was rejected.

But my idea is a bit different and also concerns about method overloading. So I decided to open a new issue. I'll be also creating another feature request soon for introducing super! keyword for overrides of methods by reopening classes.

#5583 wants the checks to be made at compile time, while I think it should be a dynamic check instead.

For example:

class A
  def some_method(a)
    "a"
  end

  def some_method(a # Numeric)
    "a is a number"
  end

  def some_method(a, b)
    "untyped a and b"
  end

  def some_method(a, b # String)
    "typed b"
  end

  def some_method(a # String, b = 2)
    "typed a"
  end
end

class B < A
  def! some_method(*args) # overrides all overloaded methods - *args is not required for this
    if args[0].is_a? Number
      super(args[0])
    else
      'do something else'
    end
  end
end

The rule to decide over multiple alternatives should be by order:

1 - max number of better matched argument types # Float is a better match for 1.2 than Numeric
2 - max number of matched argument types
3 - max number of consecutive matched argument types

Example:

a = A.new
b = B.new

b.some_method == 'do something else'
b.some_method(1.3) == 'a is a number'
b.some_method('s') == 'do something else'
a.some_method('s') == 'typed a'
a.some_method('s', 's') == 'typed a'
a.some_method(:s, 's') == 'typed b'
a.some_method(:s) == 'a'
a.some_method(1, :s) == 'untyped a and b'

Current method and send are not affected. Argument-matching checks would happen at runtime

The goal is to make programmers happier, not be perform better.

m = a.method :some_method
m.call # raise arguments mismatch exception
m.call(:a) == 'a'

To get a specific method one could ask for it like:

m = a.method :some_method, nil, String # some_method(a, b # String)

We should also introduce "methods" for getting a list of all named methods defined:

# HTTP server dispatcher class example:

def handle_http_request(params)
  methods = controller.methods :some_method
  raise "Overloaded actions are not supported" unless methods.size == 1
  action = methods.first
  method_arguments = []
  action.arguments.each do |name, type, default_value = nil|
    hk = params.has_key? name
    (method_arguments << hk ? params[name] : default_value; next) unless hk && !type.nil?
    method_arguments << method(:bind_value, type).call params[name], type
  end
  action.call *method_arguments
end

def bind_value(value, type)
  value
end

def bind_value(value, type # Integer)
  value.to_i
end

def bind_value(value, type # Float)
  value.to_f
end

def bind_value(value, type # Numeric) # BigDecimal and Numeric would match for instance
  BigDecimal.new value
end

def bind_value(value, type # Date)
  Date.parse value
end

#...



-- 
http://bugs.ruby-lang.org/