ruby - Arrays misbehaving -

here's code:

# = array.new(3, array.new(3)) = [[nil,nil,nil],[nil,nil,nil]] a[0][0] = 1 a.each {|line| p line} 

with output:

[1, nil, nil] [nil, nil, nil] 

but using commented line:

[1, nil, nil] [1, nil, nil] [1, nil, nil] 

so why that?

the commented line assigning 3 of same reference array, change 1 array propagate across other references it.

as 2 arrays vs 3, that's matter of first line specifying 3 first parameter , specifying 2 array literals in second line.

to create nested arrays without having shared references:

a = array.new(3) {array.new(3)} 

when passed block ({...} or do ... end), array.new call block obtain value of each element of array.