Array::uniq { block } ?

[Martin DeMello]

module Enumerable
def uniq_by
h = {}; inject([]) {|a,x| h[yield(x)] ||= a << x}
end
end
=> [2, 7, 9]

Beautiful about this version is that it does not need the "; h" at the end
of the inject block and no ".values", too...

Very nice indeed.

martin

 

[Florian Gross]

Also (as optimization) you could use "state << item" instead of "state +
[item]" because Array#<< returns self. This saves you a lot temporary
1element arrays and avoids creating new arrays all the time (Array#+
creates a new Array).

I dislike having the block of .inject having side effects. That sort of
defeats the purpose IMHO.

 

[David A. Black]

Hi --

Also (as optimization) you could use "state << item" instead of "state +
[item]" because Array#<< returns self. This saves you a lot temporary
1element arrays and avoids creating new arrays all the time (Array#+
creates a new Array).

I dislike having the block of .inject having side effects. That sort of
defeats the purpose IMHO.

I don't think it's a side effect, since it's just injecting something
into the accumulator or "injectee". This might be exactly what you
want if, for example, you have multiple references to the accumulator:

x = []
y = x

["a","b","c"].inject(x) {|m,n| m << n.upcase}

puts y # ["A", "B", "C"]

Otherwise in a case like this you could just use #map.


David