( scratchpad ) USE: sets ( scratchpad ) HS{ 2 5 4 3 } HS{ 5 6 7 } union . HS{ 2 3 4 5 6 7 } ( scratchpad ) HS{ 2 5 4 3 } HS{ 5 6 7 } intersect . HS{ 5 } ( scratchpad ) HS{ 2 5 4 3 } HS{ 5 6 7 } diff . HS{ 2 3 4 } ( scratchpad ) HS{ 2 5 4 3 } HS{ 5 6 7 } subset? . f ( scratchpad ) HS{ 5 6 } HS{ 5 6 7 } subset? . t ( scratchpad ) HS{ 5 6 } HS{ 5 6 7 } set= . f ( scratchpad ) HS{ 6 5 7 } HS{ 5 6 7 } set= . t