Probabilistic Programming with Scala – Hello World

import com.cra.figaro.language.{Flip, Select} //#A 
import com.cra.figaro.library.compound.If //#A 
import com.cra.figaro.algorithm.factored.VariableElimination //#A

object HelloWorld {
 val sunnyToday = Flip(0.2) //#B 
 val greetingToday = If(sunnyToday, //#C
 Select(0.6 -> "Hello world!", 0.4 -> "Howdy, universe!"), //#C
 Select(0.2 -> "Hello world!", 0.8 -> "Oh no, not again")) //#C 
 val sunnyTomorrow = If(sunnyToday, Flip(0.8), Flip(0.05)) //#D 
 val greetingTomorrow = If(sunnyTomorrow, //#E
 Select(0.6 -> "Hello world!", 0.4 -> "Howdy, universe!"), //#E 
 Select(0.2 -> "Hello world!", 0.8 -> "Oh no, not again")) //#E

 def predict() {
 val algorithm = VariableElimination(greetingToday) //#F 
 algorithm.start() //#G 
 val result =
 algorithm.probability(greetingToday, "Hello world!") //#H 
 println("Tomorrow's greeting is \"Hello world!\" " +
 "with probability " + result + ".") //#I } algorithm.kill() //#J
 }

 def infer() {
 greetingToday.observe("Hello world!") //#K 
 val algorithm = VariableElimination(sunnyToday) //#F 
 algorithm.start() //#G 
 val result = algorithm.probability(sunnyToday, true) //#H 
 println("If today's greeting is \"Hello world!\", today’s " +
 "weather is sunny with probability " + result + ".") //#I 
 algorithm.kill() //#I
 greetingToday.unobserve() //#L
 }

 def learnAndPredict() {
 greetingToday.observe("Hello world!") //#K 
 val algorithm = VariableElimination(greetingTomorrow) //#F 
 algorithm.start() //#G 
 val result =
 algorithm.probability(greetingTomorrow, "Hello world!") //#H 
 println("If today's greeting is \"Hello world!\", " +
 "tomorrow's greeting will be \"Hello world!\" " +
 "with probability " + result + ".") //#I 
 algorithm.kill() //#J 
 greetingToday.unobserve() //#L
 }

 def main(args: Array[String]) { //#M 
 predict() //#M 
 infer() //#M
 learnAndPredict() //#M
 }
}