From: "James M. Lawrence" <quixoticsycophant@...>
Date: 2008-12-11T12:53:10+09:00
Subject: Re: P shows object values, so can u put P and value in txt?


I'd like to randomly interject the under-appreciated technique of 
printing an expression and its value, as opposed just the value.

def show(&block)
  expression = block.call.strip
  result = eval(expression, block.binding)
  printf("%-20s #=> %s\n", expression, result.inspect)
end

An example using the Array#slice docs,

a = [ "a", "b", "c", "d", "e" ]
show {%{ a[2] + a[0] + a[1] }}
show {%{ a[6] }}
show {%{ a[1, 2] }}
show {%{ a[1..3] }}
show {%{ a[4..7] }}
show {%{ a[6..10] }}
show {%{ a[-3, 3] }}

verbatim output:
a[2] + a[0] + a[1]   #=> "cab"
a[6]                 #=> nil
a[1, 2]              #=> ["b", "c"]
a[1..3]              #=> ["b", "c", "d"]
a[4..7]              #=> ["e"]
a[6..10]             #=> nil
a[-3, 3]             #=> ["c", "d", "e"]

(Binding#of_caller could be used to circumvent the need for the block, 
but that has problems of its own.)
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