>>>>> "J" == Joseph McDonald <joe / vpop.net> writes:

J> Do you think Array#- should do the hash trick internally instead of a
J> complete scan x*y times ?  I do.

 It can't : the "hash trick" use #eql? and #hash
            Array#- use #==

pigeon% ruby -e 'a={{1=>1}=>1}; b = {1=>1}; p a[b]; p (a.keys - [b])'
nil
[]
pigeon% 


 Unrelated but

>>>>> "M" == Martin Pirker <crf / sbox.tu-graz.ac.dfgdfhjhzjgfdfsddadshrhdrhdfdsasaff.at> writes:

M> (as for shell tools, I first tried the grep way, but it chokes on the size
M> with a "reg.exp. too large")

 For shell tools

  comm -23 file1 file2


Guy Decoux