operator - { associativity left precedence } Declarations func -(_: Double, rhs: Double) Subtracts one value from another and produces their difference, rounded to a representable value. The subtraction operator (-) calculates the difference of its two arguments. For example: let x = 7.5 let y = x - 2.25 // y == 5.25 The - operator implements the subtraction operation defined by the IEEE 754 specification. Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: Double, rhs: Double) -> Double func -(_: Float, rhs: Float) Subtracts one value from another and produces their difference, rounded to a representable value. The subtraction operator (-) calculates the difference of its two arguments. For example: let x = 7.5 let y = x - 2.25 // y == 5.25 The - operator implements the subtraction operation defined by the IEEE 754 specification. Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: Float, rhs: Float) -> Float func -(_: Float80, rhs: Float80) Subtracts one value from another and produces their difference, rounded to a representable value. The subtraction operator (-) calculates the difference of its two arguments. For example: let x = 7.5 let y = x - 2.25 // y == 5.25 The - operator implements the subtraction operation defined by the IEEE 754 specification. Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: Float80, rhs: Float80) -> Float80 func -(_: Int, rhs: Int) Subtracts one value from another and produces their difference. The subtraction operator (-) calculates the difference of its two arguments. For example: 8 - 3 // 5 -10 - 5 // -15 100 - -5 // 105 10.5 - 100.0 // -89.5 You cannot use - with arguments of different types. To subtract values of different types, convert one of the values to the other value's type. let x: UInt8 = 21 let y: UInt = 1000000 y - UInt(x) // 999979 The difference of the two arguments must be representable in the arguments' type. In the following example, the result of 21 - 50 is less than zero, the minimum representable UInt8 value: x - 50 // Overflow error Note: Overflow checking is not performed in -Ounchecked builds. If you want to opt out of overflow checking and ignore any overflow, use the overflow subtraction operator (&-). x &- 50 // 227 Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: Int, rhs: Int) -> Int func -(_: Int8, rhs: Int8) Subtracts one value from another and produces their difference. The subtraction operator (-) calculates the difference of its two arguments. For example: 8 - 3 // 5 -10 - 5 // -15 100 - -5 // 105 10.5 - 100.0 // -89.5 You cannot use - with arguments of different types. To subtract values of different types, convert one of the values to the other value's type. let x: UInt8 = 21 let y: UInt = 1000000 y - UInt(x) // 999979 The difference of the two arguments must be representable in the arguments' type. In the following example, the result of 21 - 50 is less than zero, the minimum representable UInt8 value: x - 50 // Overflow error Note: Overflow checking is not performed in -Ounchecked builds. If you want to opt out of overflow checking and ignore any overflow, use the overflow subtraction operator (&-). x &- 50 // 227 Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: Int8, rhs: Int8) -> Int8 func -(_: Int16, rhs: Int16) Subtracts one value from another and produces their difference. The subtraction operator (-) calculates the difference of its two arguments. For example: 8 - 3 // 5 -10 - 5 // -15 100 - -5 // 105 10.5 - 100.0 // -89.5 You cannot use - with arguments of different types. To subtract values of different types, convert one of the values to the other value's type. let x: UInt8 = 21 let y: UInt = 1000000 y - UInt(x) // 999979 The difference of the two arguments must be representable in the arguments' type. In the following example, the result of 21 - 50 is less than zero, the minimum representable UInt8 value: x - 50 // Overflow error Note: Overflow checking is not performed in -Ounchecked builds. If you want to opt out of overflow checking and ignore any overflow, use the overflow subtraction operator (&-). x &- 50 // 227 Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: Int16, rhs: Int16) -> Int16 func -(_: Int32, rhs: Int32) Subtracts one value from another and produces their difference. The subtraction operator (-) calculates the difference of its two arguments. For example: 8 - 3 // 5 -10 - 5 // -15 100 - -5 // 105 10.5 - 100.0 // -89.5 You cannot use - with arguments of different types. To subtract values of different types, convert one of the values to the other value's type. let x: UInt8 = 21 let y: UInt = 1000000 y - UInt(x) // 999979 The difference of the two arguments must be representable in the arguments' type. In the following example, the result of 21 - 50 is less than zero, the minimum representable UInt8 value: x - 50 // Overflow error Note: Overflow checking is not performed in -Ounchecked builds. If you want to opt out of overflow checking and ignore any overflow, use the overflow subtraction operator (&-). x &- 50 // 227 Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: Int32, rhs: Int32) -> Int32 func -(_: Int64, rhs: Int64) Subtracts one value from another and produces their difference. The subtraction operator (-) calculates the difference of its two arguments. For example: 8 - 3 // 5 -10 - 5 // -15 100 - -5 // 105 10.5 - 100.0 // -89.5 You cannot use - with arguments of different types. To subtract values of different types, convert one of the values to the other value's type. let x: UInt8 = 21 let y: UInt = 1000000 y - UInt(x) // 999979 The difference of the two arguments must be representable in the arguments' type. In the following example, the result of 21 - 50 is less than zero, the minimum representable UInt8 value: x - 50 // Overflow error Note: Overflow checking is not performed in -Ounchecked builds. If you want to opt out of overflow checking and ignore any overflow, use the overflow subtraction operator (&-). x &- 50 // 227 Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: Int64, rhs: Int64) -> Int64 func -(_: Self, rhs: Self) Subtracts one value from another and produces their difference. The subtraction operator (-) calculates the difference of its two arguments. For example: 8 - 3 // 5 -10 - 5 // -15 100 - -5 // 105 10.5 - 100.0 // -89.5 You cannot use - with arguments of different types. To subtract values of different types, convert one of the values to the other value's type. let x: UInt8 = 21 let y: UInt = 1000000 y - UInt(x) // 999979 Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: Self, rhs: Self) -> Self.Stride Declared In FixedWidthInteger func -(_: Self, rhs: Self) Subtracts one value from another and produces their difference. The subtraction operator (-) calculates the difference of its two arguments. For example: 8 - 3 // 5 -10 - 5 // -15 100 - -5 // 105 10.5 - 100.0 // -89.5 You cannot use - with arguments of different types. To subtract values of different types, convert one of the values to the other value's type. let x: UInt8 = 21 let y: UInt = 1000000 y - UInt(x) // 999979 Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: Self, rhs: Self) -> Self.Stride Declared In FixedWidthInteger func -(_: Self, rhs: Self) Subtracts one value from another and produces their difference. The subtraction operator (-) calculates the difference of its two arguments. For example: 8 - 3 // 5 -10 - 5 // -15 100 - -5 // 105 10.5 - 100.0 // -89.5 You cannot use - with arguments of different types. To subtract values of different types, convert one of the values to the other value's type. let x: UInt8 = 21 let y: UInt = 1000000 y - UInt(x) // 999979 Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: Self, rhs: Self) -> Self.Stride Declared In FixedWidthInteger func -(_: Self, rhs: Self) Subtracts one value from another and produces their difference. The subtraction operator (-) calculates the difference of its two arguments. For example: 8 - 3 // 5 -10 - 5 // -15 100 - -5 // 105 10.5 - 100.0 // -89.5 You cannot use - with arguments of different types. To subtract values of different types, convert one of the values to the other value's type. let x: UInt8 = 21 let y: UInt = 1000000 y - UInt(x) // 999979 Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: Self, rhs: Self) -> Self.Stride Declared In FixedWidthInteger func -(_: Self, rhs: Self) Subtracts one value from another and produces their difference, rounded to a representable value. The subtraction operator (-) calculates the difference of its two arguments. For example: let x = 7.5 let y = x - 2.25 // y == 5.25 The - operator implements the subtraction operation defined by the IEEE 754 specification. Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: Self, rhs: Self) -> Self.Stride Declared In BinaryFloatingPoint, Strideable func -(_: Self, rhs: Self) Subtracts one value from another and produces their difference. The subtraction operator (-) calculates the difference of its two arguments. For example: 8 - 3 // 5 -10 - 5 // -15 100 - -5 // 105 10.5 - 100.0 // -89.5 You cannot use - with arguments of different types. To subtract values of different types, convert one of the values to the other value's type. let x: UInt8 = 21 let y: UInt = 1000000 y - UInt(x) // 999979 Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: Self, rhs: Self) -> Self.Stride Declared In FixedWidthInteger func -(_: Self, rhs: Self) Subtracts one value from another and produces their difference. The subtraction operator (-) calculates the difference of its two arguments. For example: 8 - 3 // 5 -10 - 5 // -15 100 - -5 // 105 10.5 - 100.0 // -89.5 You cannot use - with arguments of different types. To subtract values of different types, convert one of the values to the other value's type. let x: UInt8 = 21 let y: UInt = 1000000 y - UInt(x) // 999979 Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: Self, rhs: Self) -> Self.Stride Declared In FixedWidthInteger func -(_: Self, rhs: Self) Subtracts one value from another and produces their difference. The subtraction operator (-) calculates the difference of its two arguments. For example: 8 - 3 // 5 -10 - 5 // -15 100 - -5 // 105 10.5 - 100.0 // -89.5 You cannot use - with arguments of different types. To subtract values of different types, convert one of the values to the other value's type. let x: UInt8 = 21 let y: UInt = 1000000 y - UInt(x) // 999979 Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: Self, rhs: Self) -> Self.Stride Declared In FixedWidthInteger func -(_: Self, rhs: Self) Declaration func -(lhs: Self, rhs: Self) -> Self.Stride Declared In Strideable func -(_: Self, rhs: Self) Subtracts one value from another and produces their difference. The subtraction operator (-) calculates the difference of its two arguments. For example: 8 - 3 // 5 -10 - 5 // -15 100 - -5 // 105 10.5 - 100.0 // -89.5 You cannot use - with arguments of different types. To subtract values of different types, convert one of the values to the other value's type. let x: UInt8 = 21 let y: UInt = 1000000 y - UInt(x) // 999979 Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: Self, rhs: Self) -> Self.Stride Declared In FixedWidthInteger func -(_: Self, rhs: Self) Subtracts one value from another and produces their difference. The subtraction operator (-) calculates the difference of its two arguments. For example: 8 - 3 // 5 -10 - 5 // -15 100 - -5 // 105 10.5 - 100.0 // -89.5 You cannot use - with arguments of different types. To subtract values of different types, convert one of the values to the other value's type. let x: UInt8 = 21 let y: UInt = 1000000 y - UInt(x) // 999979 Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: Self, rhs: Self) -> Self.Stride Declared In FixedWidthInteger func -(_: Self, rhs: Self) Declaration func -(lhs: Self, rhs: Self) -> Self.Stride Declared In Strideable func -(_: Self, rhs: Self) Subtracts one value from another and produces their difference. The subtraction operator (-) calculates the difference of its two arguments. For example: 8 - 3 // 5 -10 - 5 // -15 100 - -5 // 105 10.5 - 100.0 // -89.5 You cannot use - with arguments of different types. To subtract values of different types, convert one of the values to the other value's type. let x: UInt8 = 21 let y: UInt = 1000000 y - UInt(x) // 999979 Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: Self, rhs: Self) -> Self.Stride Declared In FixedWidthInteger func -(_: Self, rhs: Self) Declaration func -(lhs: Self, rhs: Self) -> Self.Stride Declared In Strideable func -(_: Self, rhs: Self) Declaration func -(lhs: Self, rhs: Self) -> Self.Stride Declared In Strideable func -(_: Self, rhs: Self) Declaration func -(lhs: Self, rhs: Self) -> Self.Stride Declared In Strideable func -(_: Self, rhs: Self.Stride) Subtracts one value from another and produces their difference. The subtraction operator (-) calculates the difference of its two arguments. For example: 8 - 3 // 5 -10 - 5 // -15 100 - -5 // 105 10.5 - 100.0 // -89.5 You cannot use - with arguments of different types. To subtract values of different types, convert one of the values to the other value's type. let x: UInt8 = 21 let y: UInt = 1000000 y - UInt(x) // 999979 Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: Self, rhs: Self.Stride) -> Self Declared In FixedWidthInteger func -(_: Self, rhs: Self.Stride) Subtracts one value from another and produces their difference. The subtraction operator (-) calculates the difference of its two arguments. For example: 8 - 3 // 5 -10 - 5 // -15 100 - -5 // 105 10.5 - 100.0 // -89.5 You cannot use - with arguments of different types. To subtract values of different types, convert one of the values to the other value's type. let x: UInt8 = 21 let y: UInt = 1000000 y - UInt(x) // 999979 Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: Self, rhs: Self.Stride) -> Self Declared In FixedWidthInteger func -(_: Self, rhs: Self.Stride) Declaration func -(lhs: Self, rhs: Self.Stride) -> Self Declared In Strideable func -(_: Self, rhs: Self.Stride) Subtracts one value from another and produces their difference. The subtraction operator (-) calculates the difference of its two arguments. For example: 8 - 3 // 5 -10 - 5 // -15 100 - -5 // 105 10.5 - 100.0 // -89.5 You cannot use - with arguments of different types. To subtract values of different types, convert one of the values to the other value's type. let x: UInt8 = 21 let y: UInt = 1000000 y - UInt(x) // 999979 Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: Self, rhs: Self.Stride) -> Self Declared In FixedWidthInteger func -(_: Self, rhs: Self.Stride) Declaration func -(lhs: Self, rhs: Self.Stride) -> Self Declared In Strideable func -(_: Self, rhs: Self.Stride) Subtracts one value from another and produces their difference. The subtraction operator (-) calculates the difference of its two arguments. For example: 8 - 3 // 5 -10 - 5 // -15 100 - -5 // 105 10.5 - 100.0 // -89.5 You cannot use - with arguments of different types. To subtract values of different types, convert one of the values to the other value's type. let x: UInt8 = 21 let y: UInt = 1000000 y - UInt(x) // 999979 Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: Self, rhs: Self.Stride) -> Self Declared In FixedWidthInteger func -(_: Self, rhs: Self.Stride) Subtracts one value from another and produces their difference. The subtraction operator (-) calculates the difference of its two arguments. For example: 8 - 3 // 5 -10 - 5 // -15 100 - -5 // 105 10.5 - 100.0 // -89.5 You cannot use - with arguments of different types. To subtract values of different types, convert one of the values to the other value's type. let x: UInt8 = 21 let y: UInt = 1000000 y - UInt(x) // 999979 Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: Self, rhs: Self.Stride) -> Self Declared In FixedWidthInteger func -(_: Self, rhs: Self.Stride) Subtracts one value from another and produces their difference. The subtraction operator (-) calculates the difference of its two arguments. For example: 8 - 3 // 5 -10 - 5 // -15 100 - -5 // 105 10.5 - 100.0 // -89.5 You cannot use - with arguments of different types. To subtract values of different types, convert one of the values to the other value's type. let x: UInt8 = 21 let y: UInt = 1000000 y - UInt(x) // 999979 Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: Self, rhs: Self.Stride) -> Self Declared In FixedWidthInteger func -(_: Self, rhs: Self.Stride) Subtracts one value from another and produces their difference, rounded to a representable value. The subtraction operator (-) calculates the difference of its two arguments. For example: let x = 7.5 let y = x - 2.25 // y == 5.25 The - operator implements the subtraction operation defined by the IEEE 754 specification. Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: Self, rhs: Self.Stride) -> Self Declared In BinaryFloatingPoint, Strideable func -(_: Self, rhs: Self.Stride) Subtracts one value from another and produces their difference. The subtraction operator (-) calculates the difference of its two arguments. For example: 8 - 3 // 5 -10 - 5 // -15 100 - -5 // 105 10.5 - 100.0 // -89.5 You cannot use - with arguments of different types. To subtract values of different types, convert one of the values to the other value's type. let x: UInt8 = 21 let y: UInt = 1000000 y - UInt(x) // 999979 Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: Self, rhs: Self.Stride) -> Self Declared In FixedWidthInteger func -(_: Self, rhs: Self.Stride) Declaration func -(lhs: Self, rhs: Self.Stride) -> Self Declared In Strideable func -(_: Self, rhs: Self.Stride) Subtracts one value from another and produces their difference. The subtraction operator (-) calculates the difference of its two arguments. For example: 8 - 3 // 5 -10 - 5 // -15 100 - -5 // 105 10.5 - 100.0 // -89.5 You cannot use - with arguments of different types. To subtract values of different types, convert one of the values to the other value's type. let x: UInt8 = 21 let y: UInt = 1000000 y - UInt(x) // 999979 Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: Self, rhs: Self.Stride) -> Self Declared In FixedWidthInteger func -(_: Self, rhs: Self.Stride) Declaration func -(lhs: Self, rhs: Self.Stride) -> Self Declared In Strideable func -(_: Self, rhs: Self.Stride) Subtracts one value from another and produces their difference. The subtraction operator (-) calculates the difference of its two arguments. For example: 8 - 3 // 5 -10 - 5 // -15 100 - -5 // 105 10.5 - 100.0 // -89.5 You cannot use - with arguments of different types. To subtract values of different types, convert one of the values to the other value's type. let x: UInt8 = 21 let y: UInt = 1000000 y - UInt(x) // 999979 Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: Self, rhs: Self.Stride) -> Self Declared In FixedWidthInteger func -(_: Self, rhs: Self.Stride) Declaration func -(lhs: Self, rhs: Self.Stride) -> Self Declared In Strideable func -(_: Self, rhs: Self.Stride) Subtracts one value from another and produces their difference. The subtraction operator (-) calculates the difference of its two arguments. For example: 8 - 3 // 5 -10 - 5 // -15 100 - -5 // 105 10.5 - 100.0 // -89.5 You cannot use - with arguments of different types. To subtract values of different types, convert one of the values to the other value's type. let x: UInt8 = 21 let y: UInt = 1000000 y - UInt(x) // 999979 Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: Self, rhs: Self.Stride) -> Self Declared In FixedWidthInteger func -(_: UInt, rhs: UInt) Subtracts one value from another and produces their difference. The subtraction operator (-) calculates the difference of its two arguments. For example: 8 - 3 // 5 -10 - 5 // -15 100 - -5 // 105 10.5 - 100.0 // -89.5 You cannot use - with arguments of different types. To subtract values of different types, convert one of the values to the other value's type. let x: UInt8 = 21 let y: UInt = 1000000 y - UInt(x) // 999979 The difference of the two arguments must be representable in the arguments' type. In the following example, the result of 21 - 50 is less than zero, the minimum representable UInt8 value: x - 50 // Overflow error Note: Overflow checking is not performed in -Ounchecked builds. If you want to opt out of overflow checking and ignore any overflow, use the overflow subtraction operator (&-). x &- 50 // 227 Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: UInt, rhs: UInt) -> UInt func -(_: UInt8, rhs: UInt8) Subtracts one value from another and produces their difference. The subtraction operator (-) calculates the difference of its two arguments. For example: 8 - 3 // 5 -10 - 5 // -15 100 - -5 // 105 10.5 - 100.0 // -89.5 You cannot use - with arguments of different types. To subtract values of different types, convert one of the values to the other value's type. let x: UInt8 = 21 let y: UInt = 1000000 y - UInt(x) // 999979 The difference of the two arguments must be representable in the arguments' type. In the following example, the result of 21 - 50 is less than zero, the minimum representable UInt8 value: x - 50 // Overflow error Note: Overflow checking is not performed in -Ounchecked builds. If you want to opt out of overflow checking and ignore any overflow, use the overflow subtraction operator (&-). x &- 50 // 227 Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: UInt8, rhs: UInt8) -> UInt8 func -(_: UInt16, rhs: UInt16) Subtracts one value from another and produces their difference. The subtraction operator (-) calculates the difference of its two arguments. For example: 8 - 3 // 5 -10 - 5 // -15 100 - -5 // 105 10.5 - 100.0 // -89.5 You cannot use - with arguments of different types. To subtract values of different types, convert one of the values to the other value's type. let x: UInt8 = 21 let y: UInt = 1000000 y - UInt(x) // 999979 The difference of the two arguments must be representable in the arguments' type. In the following example, the result of 21 - 50 is less than zero, the minimum representable UInt8 value: x - 50 // Overflow error Note: Overflow checking is not performed in -Ounchecked builds. If you want to opt out of overflow checking and ignore any overflow, use the overflow subtraction operator (&-). x &- 50 // 227 Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: UInt16, rhs: UInt16) -> UInt16 func -(_: UInt32, rhs: UInt32) Subtracts one value from another and produces their difference. The subtraction operator (-) calculates the difference of its two arguments. For example: 8 - 3 // 5 -10 - 5 // -15 100 - -5 // 105 10.5 - 100.0 // -89.5 You cannot use - with arguments of different types. To subtract values of different types, convert one of the values to the other value's type. let x: UInt8 = 21 let y: UInt = 1000000 y - UInt(x) // 999979 The difference of the two arguments must be representable in the arguments' type. In the following example, the result of 21 - 50 is less than zero, the minimum representable UInt8 value: x - 50 // Overflow error Note: Overflow checking is not performed in -Ounchecked builds. If you want to opt out of overflow checking and ignore any overflow, use the overflow subtraction operator (&-). x &- 50 // 227 Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: UInt32, rhs: UInt32) -> UInt32 func -(_: UInt64, rhs: UInt64) Subtracts one value from another and produces their difference. The subtraction operator (-) calculates the difference of its two arguments. For example: 8 - 3 // 5 -10 - 5 // -15 100 - -5 // 105 10.5 - 100.0 // -89.5 You cannot use - with arguments of different types. To subtract values of different types, convert one of the values to the other value's type. let x: UInt8 = 21 let y: UInt = 1000000 y - UInt(x) // 999979 The difference of the two arguments must be representable in the arguments' type. In the following example, the result of 21 - 50 is less than zero, the minimum representable UInt8 value: x - 50 // Overflow error Note: Overflow checking is not performed in -Ounchecked builds. If you want to opt out of overflow checking and ignore any overflow, use the overflow subtraction operator (&-). x &- 50 // 227 Parameters: lhs: A numeric value. rhs: The value to subtract from lhs. Declaration func -(lhs: UInt64, rhs: UInt64) -> UInt64