@@ -23,10 +23,89 @@ extension ExpressibleByIntegerLiteral
2323 }
2424}
2525
26+ //===----------------------------------------------------------------------===//
27+ //===--- AdditiveArithmetic -----------------------------------------------===//
28+ //===----------------------------------------------------------------------===//
29+
30+ // FIXME: Add doc comment.
31+ public protocol AdditiveArithmetic : Equatable {
32+ /// The zero value.
33+ ///
34+ /// - Note: Zero is the identity element for addition; for any value,
35+ /// `x + .zero == x` and `.zero + x == x`.
36+ static var zero : Self { get }
37+
38+ /// Adds two values and produces their sum.
39+ ///
40+ /// The addition operator (`+`) calculates the sum of its two arguments. For
41+ /// example:
42+ ///
43+ /// 1 + 2 // 3
44+ /// -10 + 15 // 5
45+ /// -15 + -5 // -20
46+ /// 21.5 + 3.25 // 24.75
47+ ///
48+ /// You cannot use `+` with arguments of different types. To add values of
49+ /// different types, convert one of the values to the other value's type.
50+ ///
51+ /// let x: Int8 = 21
52+ /// let y: Int = 1000000
53+ /// Int(x) + y // 1000021
54+ ///
55+ /// - Parameters:
56+ /// - lhs: The first value to add.
57+ /// - rhs: The second value to add.
58+ static func + ( lhs: Self , rhs: Self ) -> Self
59+
60+ /// Adds two values and stores the result in the left-hand-side variable.
61+ ///
62+ /// - Parameters:
63+ /// - lhs: The first value to add.
64+ /// - rhs: The second value to add.
65+ static func += ( lhs: inout Self , rhs: Self )
66+
67+ /// Subtracts one value from another and produces their difference.
68+ ///
69+ /// The subtraction operator (`-`) calculates the difference of its two
70+ /// arguments. For example:
71+ ///
72+ /// 8 - 3 // 5
73+ /// -10 - 5 // -15
74+ /// 100 - -5 // 105
75+ /// 10.5 - 100.0 // -89.5
76+ ///
77+ /// You cannot use `-` with arguments of different types. To subtract values
78+ /// of different types, convert one of the values to the other value's type.
79+ ///
80+ /// let x: UInt8 = 21
81+ /// let y: UInt = 1000000
82+ /// y - UInt(x) // 999979
83+ ///
84+ /// - Parameters:
85+ /// - lhs: A numeric value.
86+ /// - rhs: The value to subtract from `lhs`.
87+ static func - ( lhs: Self , rhs: Self ) -> Self
88+
89+ /// Subtracts the second value from the first and stores the difference in the
90+ /// left-hand-side variable.
91+ ///
92+ /// - Parameters:
93+ /// - lhs: A numeric value.
94+ /// - rhs: The value to subtract from `lhs`.
95+ static func -= ( lhs: inout Self , rhs: Self )
96+ }
97+
98+ public extension AdditiveArithmetic where Self : ExpressibleByIntegerLiteral {
99+ static var zero : Self {
100+ return 0
101+ }
102+ }
103+
26104//===----------------------------------------------------------------------===//
27105//===--- Numeric ----------------------------------------------------------===//
28106//===----------------------------------------------------------------------===//
29107
108+ // FIXME: Update comment based on the `AdditiveArithmetic` change.
30109/// Declares methods backing binary arithmetic operators--such as `+`, `-` and
31110/// `*`--and their mutating counterparts.
32111///
@@ -61,7 +140,7 @@ extension ExpressibleByIntegerLiteral
61140/// the required mutating methods. Extensions to `Numeric` provide default
62141/// implementations for the protocol's nonmutating methods based on the
63142/// mutating variants.
64- public protocol Numeric : Equatable , ExpressibleByIntegerLiteral {
143+ public protocol Numeric : AdditiveArithmetic , ExpressibleByIntegerLiteral {
65144 /// Creates a new instance from the given integer, if it can be represented
66145 /// exactly.
67146 ///
@@ -100,65 +179,6 @@ public protocol Numeric : Equatable, ExpressibleByIntegerLiteral {
100179 /// instead of the `magnitude` property is encouraged.
101180 var magnitude : Magnitude { get }
102181
103- /// Adds two values and produces their sum.
104- ///
105- /// The addition operator (`+`) calculates the sum of its two arguments. For
106- /// example:
107- ///
108- /// 1 + 2 // 3
109- /// -10 + 15 // 5
110- /// -15 + -5 // -20
111- /// 21.5 + 3.25 // 24.75
112- ///
113- /// You cannot use `+` with arguments of different types. To add values of
114- /// different types, convert one of the values to the other value's type.
115- ///
116- /// let x: Int8 = 21
117- /// let y: Int = 1000000
118- /// Int(x) + y // 1000021
119- ///
120- /// - Parameters:
121- /// - lhs: The first value to add.
122- /// - rhs: The second value to add.
123- static func + ( lhs: Self , rhs: Self ) -> Self
124-
125- /// Adds two values and stores the result in the left-hand-side variable.
126- ///
127- /// - Parameters:
128- /// - lhs: The first value to add.
129- /// - rhs: The second value to add.
130- static func += ( lhs: inout Self , rhs: Self )
131-
132- /// Subtracts one value from another and produces their difference.
133- ///
134- /// The subtraction operator (`-`) calculates the difference of its two
135- /// arguments. For example:
136- ///
137- /// 8 - 3 // 5
138- /// -10 - 5 // -15
139- /// 100 - -5 // 105
140- /// 10.5 - 100.0 // -89.5
141- ///
142- /// You cannot use `-` with arguments of different types. To subtract values
143- /// of different types, convert one of the values to the other value's type.
144- ///
145- /// let x: UInt8 = 21
146- /// let y: UInt = 1000000
147- /// y - UInt(x) // 999979
148- ///
149- /// - Parameters:
150- /// - lhs: A numeric value.
151- /// - rhs: The value to subtract from `lhs`.
152- static func - ( lhs: Self , rhs: Self ) -> Self
153-
154- /// Subtracts the second value from the first and stores the difference in the
155- /// left-hand-side variable.
156- ///
157- /// - Parameters:
158- /// - lhs: A numeric value.
159- /// - rhs: The value to subtract from `lhs`.
160- static func -= ( lhs: inout Self , rhs: Self )
161-
162182 /// Multiplies two values and produces their product.
163183 ///
164184 /// The multiplication operator (`*`) calculates the product of its two
@@ -327,7 +347,7 @@ public func abs<T : SignedNumeric & Comparable>(_ x: T) -> T {
327347 return x < ( 0 as T ) ? - x : x
328348}
329349
330- extension Numeric {
350+ extension AdditiveArithmetic {
331351 /// Returns the given number unchanged.
332352 ///
333353 /// You can use the unary plus operator (`+`) to provide symmetry in your
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