Hi everyone!! I created an algorithm that doesn't accept any characters from a user, but numbers. I am aware of overflowing.
The question: The algorithm doesn't seem to be compact and efficient. How can I make it more readable, compact, and effective( in terms of memory )? Thank you in advance.
1). You need to test for "-" (and "+" for that matter) only on the first character. The way you have it, "12-34" will pass your tests, and +123 will not.
2). You could re-cast it like so:
...
inPut = readLine()
var noLetters : Bool
repeat {
noLetters = true
for character in inPut {
guard legalCharacter(character) else {
print("Sorry, numbers only.")
noLetters = false
break;
}
}
} while ! noLetters
...
where legalCharacter is a hypothetical function that tests for legality, taking into account a leading '-' or '+' and flagging as illegal if '-' or '+' is found in middle or end of string.
I came up with a new simple way. Perhaps, some beginners might need it. This way lets me avoid repetition, overflowing, and misleading with negative as well as positive numbers' signs in the middle of a number entered.
var noCharacters: Bool = true
var numberOnly: Int
repeat {
print("Enter the second number")
numberOnly = Int(readLine() ?? "-1") ?? -1
if numberOnly == -1 {
print("Sorry you have dialed the wrong number.\nTry again.")
noCharacters = false
}
else {
noCharacters = true
}
}
while noCharacters != true
print("You have entered \(numberOnly)")
You can avoid using -1 as a flag for wrongness by simply checking for nilness. If both readLine() is nil and Int applied to it is nil, you can ask the user to retype the number. You can also avoid the noCharacters flag:
print("Enter an integer")
while true {
if let line = readLine(), let integer = Int(line) {
print("You have entered \(integer)")
break
} else {
print("That's not an integer.\nTry again.")
}
}
The if let statement lets you do two things at once: check if the variable is not nil and, if that's the case, declare a new variable storing its unwrapped value.
if let line = readLine() {
print(line)
}
// equivalent to:
let optionalLine = readLine()
if optionalLine != nil {
let line = optionalLine!
print(line)
}
as a general rule, for any language, not just Swift, choosing a value within your range of discourse (in your case, "-1" in the set of integers) as a flag leads to the question: What if the user wanted to enter a "-1"?. You then have to handle the case. Trapping on "nil" from readline() as suggested addresses that problem.
Yeah, In a week of studying, I realize the code is garbage. This is a note for myself.
The updated version is below.
At least I feel progress daily.
var input: String?
var acceptedNumbers = "1234567890"
var noChar: Bool = false
repeat
{
input = readLine()
for character in input!
{
if acceptedNumbers.contains(character){
noChar = true
continue
}
else
{
print("You have dialed the wrong number.Try again!")
noChar = false
break
}
}
}
while noChar == false
