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List:       ruby-talk
Subject:    Re: Need examples comparing Ruby to Python
From:       Tobias Nurmiranta <spyck () lysator ! liu ! se>
Date:       2004-02-25 8:34:56
Message-ID: Pine.GSO.4.51L2.0402250910140.25026 () nazgul ! lysator ! liu ! se
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Hi,

On Wed, 25 Feb 2004, Jim Weirich wrote:
> The Python and Scheme examples are a bit different.

Yes, thats why I had a comment in the scheme code.

> The Scheme version in Ruby ...
>
>   oneplus = lambda {|x| x+1 }
>   def compose(f, g)
>     lambda { |x| f[g[x]] }
>   end
>   compose(oneplus, oneplus) [1]   #=> 3

Ah interesting, so one can use f[x] instead of f.call(x), by defining []
in Method. But if you want to call compose with defined functions instead
of lambdas, you have to use:
     compose(method(:f1), method(:f2))

I guess that this syntax "overhead" is due to that we want to be able to
call function f with "f" instead of "f()". Otherwise functions could be
passed as arguments more easily, with one syntax to call them.

Given "oneplus = lambda {|x| x + 1}" wouldn't it be possible to call the
function with "oneplus(1)", implemented so that the interpreter checks if
it is a Method instance, and then calls the method. Then you wouldn't have
to have several ways to call a function.

> The Python version of compose is more like this ...
>
>   def compose(f, g, x)
>     f[g[x]]
>   end

My python interpreter (2.3.2) doesn't accept this code.
,	Tobias

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