symbolTable: @'a'..'z'

encodeWord: function [s][
    symt: new symbolTable
    result: []
    loop s 'c [
        idx: index symt c
        'result ++ idx
        symt: (rotate symt\[0..idx] 1) ++ symt\[(idx+1)..dec size symt]
    ]
    return result
]

decodeWord: function [s][
    symt: new symbolTable
    result: []
    loop s 'idx [
        'result ++ symt\[idx]
        symt: (rotate symt\[0..idx] 1) ++ symt\[(idx+1)..dec size symt]
    ]
    return join result
]

loop ["broood", "babanaaa", "hiphophiphop"] 'word [
    encoded: encodeWord word
    decoded: decodeWord encoded
    print ["'"++word++"'" "encodes to" encoded "which correctly decodes to" "'"++decoded++"'"]
]