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  1. object SymbolicExpressions {
  2. 	type Variable = () => Unit
  3. 	type Context = Variable => Float
  4. 	type Expression = Context => Float
  5. 	type Operator = (Expression, Expression) => Expression
  6.  
  7. 	def variable = () => ()
  8.  
  9. 	def value(variable: Variable)(context: Context) = context(variable)
  10.  
  11. 	def constant(value: Float)(context: Context) = value
  12.  
  13. 	def operator(floatOperator: (Float, Float) => Float)(a: Expression, b: Expression)(context: Context) = {
  14. 	  floatOperator(a(context), b(context))
  15. 	}
  16.  
  17. 	val plus: Operator = operator(_ + _)
  18. 	val minus: Operator = operator(_ - _)
  19. 	val multiply: Operator = operator(_ * _)
  20. 	val divide: Operator = operator(_ / _)
  21. }
  22.  
  23. object Main extends App {
  24. 	import SymbolicExpressions._
  25.  
  26. 	def sqrt(x: Expression)(context: Context) = math.sqrt(x(context)).toFloat
  27.  
  28. 	val a = variable
  29. 	val b = variable
  30. 	val c = variable
  31. 	val d = variable
  32.  
  33. 	val expression = plus(minus(multiply(divide(value(a), value(b)), value(c)), value(d)), sqrt(constant(25f)))
  34.  
  35. 	val context = Map(a -> 1f, b -> 2f, c -> 3f, d -> 4f)
  36. 	println(expression(context))
  37. }
Success #stdin #stdout 0.43s 322432KB
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2.5
https://ideone.com/IwsJq1
language:
Scala (scala 2.12.8)
created:
8 years ago
visibility:
secret

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