From: Glenn <glenn_ritz@...>
Date: 2008-06-12T04:21:35+09:00
Subject: Keyword parameters

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Hi everyone,

I have a question about keyword parameters in Ruby.  I know that v1.8.6 doesn't do this and v1.9 does, and that you can 'trick' v1.8.6 into doing it with hashes.

My question is whether you can do this code:

def aProc(options = {})
  a = options[:a] || 5
  b = options[:b] || 6
  c = options[:c] || 7
  print a, b, c
end

in such a way where you wouldn't have to explicitly say that the local variable a is equal to the value in the hash with symbol :a?  In other words, to do something like iterate through the hash and turn all of the symbol keys into local variable with their respective values?

Thanks,

Glenn
 

----- Original Message ----
From: Jason Roelofs <jameskilton@gmail.com>
To: ruby-talk ML <ruby-talk@ruby-lang.org>
Sent: Monday, March 3, 2008 4:36:49 PM
Subject: Re: Why is this not implemented in Ruby

Show me a language that does allow you to do this, I've never seen it.
Even then, Ruby doesn't deal with method overloads via parameter
lists, so there's a fundamental reason why it won't work:

def foo(a)
end

def foo(a, b)
end

def foo(a, b, c)
end

foo(1) # => ArgumentError: wrong number of arguments (1 for 3)


Ruby 1.9 has keyword arguments, so you'll be able to get past that
easily then. You can fake it in 1.8 with a hash:

def aProc(options = {})
  a = options[:a] || 5
  b = options[:b] || 6
  c = options[:c] || 7
  print a, b, c
end

aProc(:a => 1, :c => 3)

With Ruby 1.9 that will look like (I think, doing this from memory):

aProc(a: 1, c: 3)

Jason

On Mon, Mar 3, 2008 at 4:27 PM, Damjan Rems <d_rems@yahoo.com> wrote:
>
>  It is probably a good reason but why is this not implemented in ruby.
>
>  irb(main):005:0> def aProc(a=5,b=6,c=7)
>  irb(main):006:1> print a,b,c
>  irb(main):007:1> end
>  irb(main):008:0> aProc
>  567=> nil
>
>  irb(main):009:0> aProc(1,,3)
>  SyntaxError: compile error
>  (irb):9: syntax error, unexpected ','
>  aProc(1,,3)
>          ^
>         from (irb):9
>         from :0
>
>  Why oh why I can not omit parameter in the middle of statement? I am
>  forced to know its default value if I want to omit a parameter in the
>  middle or at the begining of the statement.
>
>
>  by
>  TheR
>  --
>  Posted via http://www.ruby-forum.com/.
>
>
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