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  1. object SymbolicExpressions {
  2. 	type Context = Map[Variable, Float]
  3.  
  4. 	trait Expression {
  5. 		def result(context: Context): Float
  6. 	}
  7.  
  8. 	class Variable extends Expression {
  9. 		def result(context: Context) = context(this)
  10. 	}
  11.  
  12. 	class Constant(value: Float) extends Expression {
  13. 		def result(context: Context) = value
  14. 	}
  15.  
  16. 	trait Operator extends Expression {
  17. 		protected def a: Expression
  18. 		protected def b: Expression
  19.  
  20. 		protected def result(a: Float, b: Float): Float
  21.  
  22. 		def result(context: Context) = result(a.result(context), b.result(context))
  23. 	}
  24.  
  25. 	class Plus(protected val a: Expression, protected val b: Expression) extends Operator {
  26. 		protected def result(a: Float, b: Float): Float = a + b
  27. 	}
  28.  
  29. 	class Minus(protected val a: Expression, protected val b: Expression) extends Operator {
  30. 		protected def result(a: Float, b: Float): Float = a - b
  31. 	}
  32.  
  33. 	class Multiply(protected val a: Expression, protected val b: Expression) extends Operator {
  34. 		protected def result(a: Float, b: Float): Float = a * b
  35. 	}
  36.  
  37. 	class Divide(protected val a: Expression, protected val b: Expression) extends Operator {
  38. 		protected def result(a: Float, b: Float): Float = a / b
  39. 	}
  40. }
  41.  
  42. object Main extends App {
  43. 	import SymbolicExpressions._
  44.  
  45. 	class Sqrt(x: Expression) extends Expression {
  46. 		def result(context: Context) = math.sqrt(x.result(context)).toFloat
  47. 	}
  48.  
  49. 	val a = new Variable
  50. 	val b = new Variable
  51. 	val c = new Variable
  52. 	val d = new Variable
  53.  
  54. 	val expression = new Plus(new Minus(new Multiply(new Divide(a, b), c), d), new Sqrt(new Constant(25f)))
  55.  
  56. 	val context = Map(a -> 1f, b -> 2f, c -> 3f, d -> 4f)
  57. 	println(expression.result(context))
  58. }
Success #stdin #stdout 0.38s 322432KB
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2.5
https://ideone.com/8pCfY1
language:
Scala (scala 2.12.8)
created:
9 years ago
visibility:
secret

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