hashJoin table1 index1 table2 index2:
    local :h {}
    # hash phase
    for s in table1:
        local :key s! index1
        if not has h key:
            set-to h key []
        push-to h! key s
    # join phase
    []
    for r in table2:
        for s in copy h! r! index2:
            push-through swap [ s r ]

local :table1 [ [ 27 "Jonah" ] [ 18 "Alan" ] [ 28 "Glory" ] [ 18 "Popeye" ] [ 28 "Alan" ] ]
local :table2 [ [ "Jonah" "Whales" ] [ "Jonah" "Spiders" ] [ "Alan" "Ghosts" ] [ "Alan" "Zombies" ] [ "Glory" "Buffy" ] ]

for row in hashJoin table1 1 table2 0:
    !. row