1

I am developing my first project with Swift. Yesterday I attempted to add protocols ExpressibleByStringLiteral, ExpressibleByIntegerLiteral to a numerical class. I could get the changes to compile but could not get an object to instantiate with them and would get a fatal error when I ran the project. I could not even get the debugger to break in the two inits. Then I happen to discover the issue. If I instantiate an object of this class by any init method that are not one of these two protocols then the protocols will work fine from then on. In other words I can't use either of these two protocols first to instantiate an object of the class. Both protocol inits work perfectly when they are eventually called.

Is this a bug or am I missing something to enable the protocols? It looks like both of these protocols are depending on the fact that any instance of the class exists and has been instantiated.

Example:

This code segment works:

// all variables are APMInt
ll = APMInt(I64: 20) // instantiation that doesn't use protocol ExpressibleByStringLiteralor or ExpressibleByIntegerLiteral
ii = 3
jj = 4
print(ii * jj)
ii = "99"
jj = "88"
print (ii - jj)
kk = ii * jj

This code fails:

// all variables are APMInt
ii = 3
jj = 4
print(ii * jj)
ii = "99"
jj = "88"
print (ii - jj)
kk = ii * jj

Result:
Thread 1: EXC_BAD_ACCESS (code=2, address=0x7fff5965dea8) on line with print(ii * jj) because the objects ii and jj are garbage since they did not really go through their inits

2

Please post the code for APMInt, including the initializers for the protocols.

Also, when you post code on this forum, please put triple back-ticks (```) on the lines before and after it, so it shows up formatted properly.

3

Okay, the below is a stub of the class showing the inits and protocols. Not executable without a lot of the other code.

//
//  APMInt_Class.swift
//

import Foundation

let apmint_base_bits: Int = 30
let apmint_base: Int = 1 << apmint_base_bits
let apmint_lo_mask: Int = apmint_base - 1
let apmint_hi_mask: Int = ~apmint_lo_mask

// APInt Constants
let ZERO: APMInt = APMInt(I64: 0)
let ONE: APMInt = APMInt(I64: 1)
let TWO: APMInt = APMInt(I64: 2)
let THREE: APMInt = APMInt(I64: 3)
let MINUSONE: APMInt = APMInt(I64: -1)

// used to capture math errors
var apmint_error_status: Int = 0
var apmint_error_messages: [String] = [ ""
    , "Divide by Zero"
    , "Mod by Zero"
    , "Bad Bit Number"
    , "Square Root of Negative"]


extension APMInt: CustomStringConvertible {
    public var description: String {
        return self.to_string()
    }
}

class APMInt: ExpressibleByStringLiteral, ExpressibleByIntegerLiteral {
    
    var sign: Int     // -1 for negative, 0 or zero, 1 for positive
    var words: [Int]
    
    public required init(integerLiteral:Int) {
        if integerLiteral == 0 {
            self.sign = 0
            self.words = [0]
            return
        }
        
        var input: Int
        
        if integerLiteral < 0 {
            input = -integerLiteral
            self.sign = -1
        } else {
            input = integerLiteral
            self.sign = 1
        }
        
        if input <= apmint_lo_mask {
            self.words = [input]
        } else {
            self.words = [input & apmint_lo_mask] + [input >> apmint_base_bits]
        }
    }

    public required init(stringLiteral:String){
        var result = APMInt(I64: 0)
        var digit_found: Bool = false
        var sign: Int = 1
        for chars in stringLiteral.utf8 {
            if chars > 47 && chars < 58 {
                digit_found = true
                result = (result * 10) + Int(chars - 48)
            } else if chars == 45 {      // minus sign
                sign = -1
            } else if chars == 43 {      // plus sign
                sign = 1
            }
        }
        if digit_found == false || result.sign == 0 {
            self.sign = 0
            self.words = [0]
        } else {
            self.sign = sign
            self.words = result.words
        }
    }
    
    // init from Int
    init (I64: Int) {
        
        if I64 == 0 {
            self.sign = 0
            self.words = [0]
            return
        }
        
        var input: Int
        
        if I64 < 0 {
            input = -I64
            self.sign = -1
        } else {
            input = I64
            self.sign = 1
        }
        
        if input <= apmint_lo_mask {
            self.words = [input]
        } else {
            self.words = [input & apmint_lo_mask] + [input >> apmint_base_bits]
        }
    }
    
    // init from string
    required init (Text: String) {
        var result = APMInt(I64: 0)
        var digit_found: Bool = false
        var sign: Int = 1
        for chars in Text.utf8 {
            if chars > 47 && chars < 58 {
                digit_found = true
                result = (result * 10) + Int(chars - 48)
            } else if chars == 45 {      // minus sign
                sign = -1
            } else if chars == 43 {      // plus sign
                sign = 1
            }
        }
        if digit_found == false || result.sign == 0 {
            self.sign = 0
            self.words = [0]
        } else {
            self.sign = sign
            self.words = result.words
        }
    }
    
    
    func to_string() -> String {
        if self.words.count == 0 || self.sign == 0 {return "0"}
        var out_string: String = ""
        var temp: APMInt = self.abs()
        var digit: Int
        while temp.sign != 0 {
            digit = temp % 10
            do { temp = temp / 10}
            out_string = String(UnicodeScalar(UInt8(digit + 48))) + out_string
        }
        if self.sign == -1 {
            out_string = "-" + out_string
        }
        return out_string
    }
}