From: Charles Comstock <cc1@...>
Date: 2004-04-12T11:39:17+09:00
Subject: Re: zip block oddities/bug?

Simon Strandgaard wrote:
> When supplying a block to zip, shouldn't you
> be able to affect the output produced by #zip ?
> 
> No matter what I do it outputs 'nil'.. 
> 
> Is this the intented behavier ?
> 
> irb(main):020:0> (4..6).zip {|i| p i; nil }
> [4]
> [5]
> [6]
> => nil
> irb(main):021:0> (4..6).zip {|i| p i; [] }
> [4]
> [5]
> [6]
> => nil
> irb(main):022:0> (4..6).zip {|i| p i; 666 }
> [4]
> [5]
> [6]
> => nil
> irb(main):023:0> (4..6).zip(8) {|i| p i; 666 }
> TypeError: cannot convert Fixnum into Array
>         from (irb):23:in `zip'
>         from (irb):23
>         from :0
> irb(main):024:0> (4..6).zip(8) {|i| p i; nil }
> TypeError: cannot convert Fixnum into Array
>         from (irb):24:in `zip'
>         from (irb):24
>         from :0
> irb(main):025:0> (4..6).zip([8]) {|i| p i; nil }
> [4, 8]
> [5, nil]
> [6, nil]
> => nil
> irb(main):026:0>
> 
> Except from the last line, I only get nil outputted
> The block is mentioned in RI, but .. 
> 
> 
> erver> ri Enumerable.zip
> --------------------------------------------------------- Enumerable#zip
>      enum.zip(arg, ...)                   => array
>      enum.zip(arg, ...) {|arr| block }    => nil
> ------------------------------------------------------------------------
>      Converts any arguments to arrays, then merges elements of _enum_
>      with corresponding elements from each argument. This generates a
>      sequence of +enum#size+ _n_-element arrays, where _n_ is one more
>      that the count of arguments. If the size of any arguemnt is less
>      than +enum#size+, +nil+ values are supplied. If a block given, it
>      is invoked for each output array, otherwise an array of arrays is
>      returned.
> 
>         a = [ 4, 5, 6 ]
>         b = [ 7, 8, 9 ]
>      
>         (1..3).zip(a, b)      #=> [[1, 4, 7], [2, 5, 8], [3, 6, 9]]
>         "cat\ndog".zip([1])   #=> [["cat\n", 1], ["dog", nil]]
>         (1..3).zip            #=> [[1], [2], [3]]
> 
> server>
> 
> --
> Simon Strandgaard

irb(main):009:0> (1..3).zip([4,5,6]) {|x| p x;}
[1, 4]
[2, 5]
[3, 6]
=> nil

I don't follow why it was decided that the final result be nil, it would 
be nice if returned the results from the block, meaning the above 
example would result in:

irb(main):009:0> (1..3).zip([4,5,6]) {|x| p x; x}
[1, 4]
[2, 5]
[3, 6]
=> [[1, 4],[2, 5], [3, 6]]

But I guess that was just the original concept.

Charles Comstock