Viterbi algorithm written in MoonScript

viterbi.moon

obs = {'normal', 'cold', 'dizzy'}
states = {'Healthy', 'Fever'}
start_p = {
    Healthy: 0.6,
    Fever: 0.4
}

trans_p = {
    Healthy: {
        Healthy: 0.7,
        Fever: 0.3
    },
    Fever: {
        Healthy: 0.4,
        Fever: 0.6
    }
}

emit_p = {
    Healthy: {
        normal: 0.5,
        cold: 0.4,
        dizzy: 0.1
    },
    Fever: {
        normal: 0.1,
        cold: 0.3,
        dizzy: 0.6
    }
}

M = require 'moses'

-- viterbi algorithm
last_states = nil
path = for ob in *obs
    probFunc = unless last_states
        (state) -> start_p[state] * emit_p[state][ob] 
    else
        (state) -> M.max [last_states[new_state] * trans_p[state][new_state] * emit_p[new_state][ob] for new_state in *states]

    last_states = {state, probFunc state for state in *states}

    M.best(M.kvpairs(last_states), (a, b) -> a[2] > b[2])[1]

-- print result
for state in *path
    print state