From: Dan Doel <djd15@...>
Date: 2003-08-13T11:34:06+09:00
Subject: Re: hash default value

Christoph R. wrote:

> or if you like puzzles
>
> ---
> body = proc {|hsh,key| hsh[key] = Hash.new &body }
> autovhsh = Hash.new &body
>
> autovhsh[1][2][3] = 4
> p  autovhsh[1][2][3]  # => 4
> --- 

Like puzzles, do you?

$y =
proc { |f|
    proc { |x|
        f[x[x]]
    }[proc { |x|
        proc { |z,w|
            f[x[x]][z,w]
        }
    }]
}

def y(f)
    proc do |z, w|
        f[y(f)][z, w]
    end
end

gen2 = proc { |f|
    proc { |h, k|
        h[k] = Hash.new &f
    }
}

h1 = Hash.new &(y(gen2))
h2 = Hash.new &($y[gen2])

p "Using h1"
p h1['1']
p h1['a']['b']['c']

p "Using h2"

p h2['1']
p h2['a']['b']['c']['d'][4]

Fun-ctional programming with Ruby.

- Dan