From: James Coglan <jcoglan@...>
Date: 2009-03-20T18:07:22+09:00
Subject: Re: Passing a named function instead of a code block?

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2009/3/20 7stud -- <bbxx789_05ss@yahoo.com>

> Matthias Reitinger wrote:
> >
> >   puts c.collect(&method(:fib))
> >
>
> Why is there a difference here:
>
> def square1(x)
>  x*x
> end
>
> square2 = lambda { |x| x*x}
>
> puts [1, 2, 3].collect(&square2)
> puts [1, 2, 3].collect(&square1)
>
> --output:--
> 1
> 4
> 9
> r1test.rb:8:in `square1': wrong number of arguments (0 for 1)
> (ArgumentError)
>        from r1test.rb:8
>
>
> Why does ruby make you use the tortured syntax:
>
> &method(:square1)
>
> for a method vs. the easier syntax for a Proc object?



square2 is a variable name (ie. something you've made an assignment to),
it's just a reference to the lambda object. However, square1 is a method and
Ruby allows calling methods without parens, so 'square1' is actually
interpreted as a method call to square1 with no arguments. Therefore, to
grab a method as an object without calling it, we need to use
method(:square1).

--
James Coglan
http://github.com/jcoglan

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