markov_chain_text_generator.sf

#!/usr/bin/ruby

# A very simple text generator, using Markov chains.

# See also:
#   https://en.wikipedia.org/wiki/Markov_chain
#   https://rosettacode.org/wiki/Markov_chain_text_generator

func build_dict (n, words) {
    var dict = Hash()
    words.each_cons(n+1, {|*prefix|
        var suffix = prefix.pop
        dict{prefix.join(' ')} := [] << suffix
    })
    return dict
}

var file = File(ARGV[0] || "alice_oz.txt")
var n    =  Num(ARGV[1] || 2)
var max  =  Num(ARGV[2] || 100)

var words = file.open_r.words
words << words.first(n)...

var dict = build_dict(n, words)
var rotor = words.first(n)
var chain = [rotor...]

max.times {
    var new = dict{rotor.join(' ')}.rand
    chain.push(new)
    rotor.shift
    rotor.push(new)
}

say chain.join(' ')