gistfile1.txt

// Consider a generic class where `lhs` and `rhs` can be of any numeric type
struct Operation: Printable {
    let lhs: Float
    let rhs: Float
    let `operator`: Operator
    
    var description: String {
        return "\(lhs) \(`operator`.symbol) \(rhs)"
    }
}

// Create an equation
let equation = "5 + 3 * 6 - ( 5 / 3 ) + 7"

// Create a MathSolver
let solver = MathSolver()

// Pass the equation to the `solve` method.
let steps = solver.solve(equation)

/**
The solve method outputs an array of `Operation`s:

 3.0 * 6.0 = 18.0
 5.0 + 18.0 = 23.0
 5.0 / 3.0 = 1.66667
 23.0 - 1.66667 = 21.3333
 21.3333 + 7.0 = 28.3333
 
 There are slight issues with "linking" operations, that is, establishing which number came from the previous step and how to explain it to students.
 
 We could also change the output of `solve` to output a `Solution` object, which may look like this:
 
 struct Solution {
   var operations: [Operation]
   var solution: Float
 }
 */