import Foundation
/*
============================================================
Convert a decimal-like value to Int64 in Swift.
This program demonstrates:
• Conversion using rounded(), which rounds to the nearest integer.
• Conversion using Int64(value), which truncates toward zero.
• Conversion using Decimal + NSDecimalNumber for strict conversion.
• Helper functions that print all conversion styles.
Notes:
• Swift does not have a built-in "long" type; Int64 is the closest.
• rounded() returns a Double; cast to Int64 afterward.
• Int64(value) truncates the fractional part.
• Decimal → Int64 conversion is done via NSDecimalNumber.
============================================================
*/
// Rounds a Double to Int64
func convertDoubleToInt64(_ value: Double) -> Int64 {
return Int64(value.rounded())
}
// Truncates a Double to Int64
func castDoubleToInt64(_ value: Double) -> Int64 {
return Int64(value)
}
// Converts Decimal using truncation
func convertDecimalToInt64(_ value: Decimal) -> Int64 {
return NSDecimalNumber(decimal: value).int64Value
}
// Converts Decimal strictly (throws if fractional or out of range)
func convertDecimalExact(_ value: Decimal) -> String {
let number = NSDecimalNumber(decimal: value)
do {
let exact = try number.int64ValueExact()
return "\(exact)"
} catch {
return "ERROR — fractional or out of range"
}
}
// Prints conversion styles for Double
func showDoubleConversions(_ value: Double) {
print("Input decimal (Double): \(value)")
print("Rounded (rounded): \(convertDoubleToInt64(value))")
print("Truncated (Int64 cast): \(castDoubleToInt64(value))")
print()
}
// Prints conversion styles for Decimal
func showDecimalConversions(_ value: Decimal) {
print("Input decimal (Decimal): \(value)")
print("Truncated (int64Value): \(convertDecimalToInt64(value))")
print("Exact (int64ValueExact): \(convertDecimalExact(value))")
print()
}
extension NSDecimalNumber {
// Throws if fractional or out of range
func int64ValueExact() throws -> Int64 {
if self.decimalValue != Decimal(self.int64Value) {
throw NSError(domain: "ExactConversion", code: 1, userInfo: nil)
}
return self.int64Value
}
}
func main() {
// Double examples
showDoubleConversions(12.7)
showDoubleConversions(12.3)
showDoubleConversions(-5.8)
showDoubleConversions(42.0)
// Decimal examples
showDecimalConversions(Decimal(string: "12.7")!)
showDecimalConversions(Decimal(string: "42")!)
showDecimalConversions(Decimal(string: "-5.8")!)
}
// Call main manually
main()
/*
run:
Input decimal (Double): 12.7
Rounded (rounded): 13
Truncated (Int64 cast): 12
Input decimal (Double): 12.3
Rounded (rounded): 12
Truncated (Int64 cast): 12
Input decimal (Double): -5.8
Rounded (rounded): -6
Truncated (Int64 cast): -5
Input decimal (Double): 42.0
Rounded (rounded): 42
Truncated (Int64 cast): 42
Input decimal (Decimal): 12.7
Truncated (int64Value): 12
Exact (int64ValueExact): ERROR — fractional or out of range
Input decimal (Decimal): 42
Truncated (int64Value): 42
Exact (int64ValueExact): 42
Input decimal (Decimal): -5.8
Truncated (int64Value): -5
Exact (int64ValueExact): ERROR — fractional or out of range
*/
