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  1. a = %w(java ruby rust)
  2. puts a.join(',')
  3. print *a.map.with_index {|s, i| 0 < i ? ',' + s : s}, "\n"
  4. print *a.zip([','] * (a.size - 1)).flatten, "\n"
  5. a.each_with_index do |s, i|
  6. print ',' if 0 < i
  7. print s
  8. end
  9. puts
  10. def f(a)
  11. if a.size == 1
  12. a[0]
  13. else
  14. a[0] + ',' + f(a.drop 1)
  15. end
  16. end
  17. puts f a
  18.  
Success #stdin #stdout 0.01s 5940KB
stdin
Standard input is empty
stdout
java,ruby,rust
java,ruby,rust
java,ruby,rust
java,ruby,rust
java,ruby,rust