cs193p – Assignment #1 Extra Task #4

Please note, this blog entry is from a previous course. You might want to check out the current one.

Make one of your operation buttons be “generate a random number between 0 and 1”. This operation button is not a constant (since it changes each time you invoke it). Nor is it a unary operation (since it does not operate on anything).

In the interface builder change the name of a button to “rand”:

Add an operation without operands to the the calculator model:

private enum Operation {
  ...
  case NullaryOperation(() -> Double, String)
  ...
}

The “random” operation returns the function generating the random number as well as a string for its description:

private var operations: Dictionary<String,Operation> = [
  ...
  "rand" : Operation.NullaryOperation(drand48, "rand()")
]

… which are used to calculate the result and the description:

func performOperation(symbol: String) {
  ...
  case .NullaryOperation(let function, let descriptionValue):
    accumulator = function()
    descriptionAccumulator = descriptionValue
  ...
}

The complete code for the extra task #4 is available on GitHub.