gistfile1.txt

Assumptions:

I should guard against any negative doubles.

Test Cases:

1.00 --> "Your change is 1 dollar."
1.01 --> "Your change is 1 dollar and 1 penny."
1.41 --> "Your change is 1 dollar and 1 quarter and 1 dime and 1 nickel and 1 penny."


Implementation:

I will start by writing some if statements inside of a while loop. The if statements will check if I can subtract 1.00, .25,
.10, .05 and .01, beginning with the largest. I will then subtract the number from the variable within which I will save the 
amount of change due. I will also += the appropriate variable containing the number of change items that the if statement
indicates. After doing this I will work on making the code more concise and refined.

Code:

func makeChange(forAmount: Double, withCost: Double) -> String {
    guard forAmount > withCost, forAmount > 0, withCost >= 0 else {
        return "You are not due any change."
    }
    var dollars = 0
    var quarters = 0
    var dimes = 0
    var nickels = 0
    var pennies = 0
    var changeDue = forAmount - withCost
    var dollarsString = ""
    var quartersString = ""
    var dimesString = ""
    var nickelsString = ""
    var penniesString = ""
    while changeDue != 0 {
        if changeDue >= 1.00 {
            changeDue -= 1.00
            dollars += 1
        }
        else if changeDue >= 0.25 {
            changeDue -= 0.25
            quarters += 1
        }
        else if changeDue >= 0.10 {
            changeDue -= 0.10
            dimes += 1
        }
        else if changeDue >= 0.05 {
            changeDue -= 0.05
            nickels += 1
        }
        else if changeDue >= 0.01 {
            changeDue -= 0.01
            pennies += 1
        }
    }
    if dollars != 1 {
        dollarsString = "\(dollars) dollars"
    } else {
        dollarsString = "\(dollars) dollar"
    }
    if quarters != 1 {
        quartersString = "\(quarters) quarters"
    } else {
        quartersString = "\(quarters) quarter"
    }
    if dimes != 1 {
        dimesString = "\(dimes) dimes"
    } else {
        dimesString = "\(dimes) dime"
    }
    if nickels != 1 {
        nickelsString = "\(nickels) nickels"
    } else {
        nickelsString = "\(nickels) nickel"
    }
    if dollars != 1 {
        penniesString = "\(pennies) pennies"
    } else {
        penniesString = "\(pennies) penny"
    }
    
    return "Your change is \(dollarsString), \(quartersString), \(dimesString), \(nickelsString) and \(penniesString)."
}