Re: Optional arguments and default values

Ross Bamford <rosco@xxxxxxxxxxxxxxxxxxxxxx> wrote: 
On Fri, 30 Dec 2005 19:59:05 -0000, Surgeon <biyokuantum@xxxxxxxxx>
wrote:

Hi,

How do I give a method optional arguments and default values?

Exmpl:

foo is a function that multiplies all of its arguments together. If
there is not any argument, a default value of "qwerty" returns.

foo(2,3)    ---->  6
foo(2,3,5) ----> 30
foo(2,3,5,2) -> 60

foo() -----------> "qwerty"


Maybe:
def foo(*args)
  args.empty? && "qwerty" or args.inject(0) { |s,i| s * i }
end

or:

def foo(*args)
  if args.empty?
    "qwerty"
  else
    args.inject(0) { |s,i| s * i }
  end
end

The implementation of Enumerable#inject allows for an even more elegant solution

def foo(*args)
 args.inject {|a,b| a*b} || "qwerty"
end

foo 2,3,5
=> 30
foo 2,3
=> 6
foo 2
=> 2
foo 
=> "qwerty"

Note: if args is empty this inject returns nil, if there is just one element that is returned.

Another solution would be to implement things like this in Enumerable:

module Enumerable
 def sum()     inject(0) {|a,b| a+b} end
 def product() inject(1) {|a,b| a*b} end
end

or

module Enumerable
 def sum()     inject {|a,b| a+b} end
 def product() inject {|a,b| a*b} end
end

Allowing for invocations like these

[1,2,3,4].sum
=> 10
(1..4).sum
=> 10
(1...5).sum
=> 10
(1..10).map { rand 20 }.sum 
=> 91

Kind regards

   robert

.

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