Re: how to remove dups from 2 lists?

From: Mike S. [mailto:[email protected]]

I’m looking for a function that will eliminate all matching
items, like canceling terms in a fraction. If the first list
has 3 "a"s, and the second list has 5 "a"s, then afterwards
the first list should have 0 "a"s and the second list should
have 2 "a"s.

class Array
def remove_instances( *values )
result = dup
values.flatten.each{ |value|
if i = result.index( value )
result.delete_at( i )
end
}
result
end
end

a1 = %w| a a a b b c |
a2 = %w| a a a a a b |

p a1.remove_instances( a2 )
#=> [“b”, “c”]
p a2.remove_instances( a1 )
#=> [“a”, “a”]

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