From: 7stud -- <dolgun@...>
Date: 2007-10-05T12:25:25+09:00
Subject: Re: Add files to array matching pattern

Leon Bogaert wrote:
> Tried this:
> 
> dir = "/home/leon/"; test = Array.new; test = 
> Dir.new(dir).entries.collect { |x| x == 'filezilla' ? x : next  }
> 
> But that didn't work also. It gives back:
> 
> [nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, 
> nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, 
> nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, 
> nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, 
> nil, nil, nil, nil, nil, nil, nil, nil, nil]

The reason you get that output is:

1) collect adds the value returned by the block to a results array.

2) There is no file named "filezilla" in the directory /home/leon

3) That means the value of the block is always whatever is produced by 
the statement: next.  If you try this:

[1, 2, 3].each {|x| puts next}

you'll get the error

r9test.rb:1: void value expression

I think that means that the next statement is one of the few statements 
in ruby that doesn't produce a value.  So what is the value of the block 
when the next statement gets executed as the last statement?   If you 
try this:

results = [1, 2, 3].collect {|x| next}
p results

the output is:

[nil, nil, nil]

Look familiar?  Apparently, a block returns nil by default if the 
statements in the block do not produce any values.
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