`Int`

Numbers are used throughout Swift programs. With an Int, we have an integral type that can be used in expressions, collections and loops.

In Swift we find it is 8 bytes and can accommodate large numbers. It does not support fractional values. We can handle overflow with special methods.

First example

Let us run through some Int properties. First we use MemoryLayout on the Int type. This returns the byte count in an Int which is 8.

Here Max and min are useful properties on the Int. As we see in the output, an Int in Swift is like a long in other languages.

Next Advanced() adds to the Int. We can just use an add operator like "+=" for most programs.

Tip To go to the previous number, we can use advanced() by negative one. But subtracting one is likely clearer.

// Display byte size of Int.
let size = MemoryLayout<Int>.size
print(size)

// Display maximum Integer value.
let max = Int.max
print(max)

// Display minimum Integer value.
let min = Int.min
print(min)

// Use advanced to increment an Int.
var value = 100
let result = value.advanced(by: 10)
print(result)

// Use advanced to move forward and back.
let next = result.advanced(by: 1)
print(next)

let previous = result.advanced(by: -1)
print(previous)8
9223372036854775807
-9223372036854775808
110
111
109

`ReportingOverflow`

In an overflow, a number cannot be represented using the available bits. This causes a logic problem and unexpected results.

Start We try to capture overflows with multipliedReportingOverflow. We perform a multiply that causes an overflow.

Info Here the numbers multiplied do not overflow, so the "overflow" property returns false.

Tip Other "reporting overflow" methods are available. They are called in the same way as multipliedReportingOverflow.

// Part 1: do a multiply that overflows.
let res1 = Int.max.multipliedReportingOverflow(by: 2)
print(res1)

// Test whether it overflowed.
if res1.overflow {
    print("An overflow happened")
}

// Part 2: do a multiply that will not overflow.
let res2 = 2.multipliedReportingOverflow(by: 2)
print(res2)

// We did not have an overflow, so print the 0 value.
if !res2.overflow {
    print(res2.0)
}(partialValue: -2, overflow: true)
An overflow happened
(partialValue: 4, overflow: false)
4

Overflow operators

By default in Swift an overflow causes an error. With the overflow add, subtract and multiply operators, this error does not appear.

Detail The numeric value will become invalid. It will wrap around to the lowest (or highest) value.

// This number cannot be incremented without overflow.
var number = Int8.max
print(number)

// Use overflow operator to avoid an error.
// ... Add 1 to number.
number = number &+ 1
print(number)127
-128&+    Overflow addition
&-    Overflow subtraction
&*    Overflow multiplication

Convert to `String`

With the String init method, we can convert an Int into a String. This always succeeds. Every possible Int can be represented as a String.

Numbers are everywhere

Int is used in nearly every program. It is 8 bytes, which makes it similar to "long" values in other languages.

Int