markov.lua

-- help function

function allwords()
    local line = io.read() -- current line
    local pos = 1 -- current position in the line
    return function () -- iterator function
        while line do 
            local w, e = string.match(line, "(%w+[,;.:]?)()", pos)
            if w then
                pos = e
                return w
            else
                line = io.read()
                pos = 1
            end
        end
        return nil
    end
end


function prefix(w1, w2)
    return w1 .. " " .. w2
end

local statetab = {}

function insert(prefix, value)
    local list = statetab[prefix]
    if list == nil then
        statetab[prefix] = {value}
    else
        list[#list + 1] = value
    end
end

------------

-- build table
local MAXGEN = 200
local NOWORD = "\n"

local w1, w2 = NOWORD, NOWORD

for nextword in allwords() do
    insert(prefix(w1, w2), nextword)
    w1 = w2; w2 = nextword;
end
insert(prefix(w1, w2), NOWORD)

-- generate text
w1 = NOWORD; w2 = NOWORD
for i = 1, MAXGEN do
    local list = statetab[prefix(w1, w2)]
    local r = math.random(#list)
    local nextword = list[r]
    if nextword == NOWORD then
        return
    end
    io.write(nextword, " ")
    w1 = w2; w2 = nextword
end