From: "Peña, Botp" <botp@...>
Date: 2007-09-05T13:37:32+09:00
Subject: Re: assigning to hash keys when there is a default value?

From: Robert Klemme [mailto:shortcutter@googlemail.com] 
# 2007/9/4, Yossef Mendelssohn <ymendel@pobox.com>:
# > If '"x+=1" will always be "x=x+1"', what's the problem in 
# having x ||=
# > 1 always be x = x || 1?
# That an assignment of x=x is useless (basically a nop in the standard
# case of x being a variable).  

consider,

irb(main):074:0* h=Hash.new
=> {}
irb(main):075:0> h[5] = h[5]
=> nil
irb(main):076:0> h
=> {5=>nil}
irb(main):062:0* h=Hash.new(1)
=> {}
irb(main):063:0> h[5] = h[5]
=> 1
irb(main):064:0> h
=> {5=>1}

thus h[k] = h[k] could mean
    h[k] = h.default   or
    h[k] = nil

definitely not useless and not noop.

seeking enlightenment -botp