[stdlib] Implement SE-0233 AdditiveArithmetic #20422
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@@ -23,10 +23,89 @@ extension ExpressibleByIntegerLiteral | |
| } | ||
| } | ||
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| //===----------------------------------------------------------------------===// | ||
| //===--- AdditiveArithmetic -----------------------------------------------===// | ||
| //===----------------------------------------------------------------------===// | ||
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| // FIXME: Add doc comment. | ||
| public protocol AdditiveArithmetic : Equatable { | ||
| /// The zero value. | ||
| /// | ||
| /// - Note: Zero is the identity element for addition; for any value, | ||
| /// `x + .zero == x` and `.zero + x == x`. | ||
| static var zero: Self { get } | ||
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| /// Adds two values and produces their sum. | ||
| /// | ||
| /// The addition operator (`+`) calculates the sum of its two arguments. For | ||
| /// example: | ||
| /// | ||
| /// 1 + 2 // 3 | ||
| /// -10 + 15 // 5 | ||
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There was a problem hiding this comment. Examples involving the unary negative operator should probably be removed from the documentation for this protocol. There was a problem hiding this comment. Sure, but it was originally on There was a problem hiding this comment. Right. @xwu, can you open a SR bug for this (since we would want to consider it on |
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| /// -15 + -5 // -20 | ||
| /// 21.5 + 3.25 // 24.75 | ||
| /// | ||
| /// You cannot use `+` with arguments of different types. To add values of | ||
| /// different types, convert one of the values to the other value's type. | ||
| /// | ||
| /// let x: Int8 = 21 | ||
| /// let y: Int = 1000000 | ||
| /// Int(x) + y // 1000021 | ||
| /// | ||
| /// - Parameters: | ||
| /// - lhs: The first value to add. | ||
| /// - rhs: The second value to add. | ||
| static func +(lhs: Self, rhs: Self) -> Self | ||
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| /// Adds two values and stores the result in the left-hand-side variable. | ||
| /// | ||
| /// - Parameters: | ||
| /// - lhs: The first value to add. | ||
| /// - rhs: The second value to add. | ||
| static func +=(lhs: inout Self, rhs: Self) | ||
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| /// 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`. | ||
| static func -(lhs: Self, rhs: Self) -> Self | ||
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| /// Subtracts the second value from the first and stores the difference in the | ||
| /// left-hand-side variable. | ||
| /// | ||
| /// - Parameters: | ||
| /// - lhs: A numeric value. | ||
| /// - rhs: The value to subtract from `lhs`. | ||
| static func -=(lhs: inout Self, rhs: Self) | ||
| } | ||
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| public extension AdditiveArithmetic where Self : ExpressibleByIntegerLiteral { | ||
| static var zero: Self { | ||
| return 0 | ||
| } | ||
| } | ||
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| //===----------------------------------------------------------------------===// | ||
| //===--- Numeric ----------------------------------------------------------===// | ||
| //===----------------------------------------------------------------------===// | ||
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| // FIXME: Update comment based on the `AdditiveArithmetic` change. | ||
| /// Declares methods backing binary arithmetic operators--such as `+`, `-` and | ||
| /// `*`--and their mutating counterparts. | ||
| /// | ||
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@@ -61,7 +140,7 @@ extension ExpressibleByIntegerLiteral | |
| /// the required mutating methods. Extensions to `Numeric` provide default | ||
| /// implementations for the protocol's nonmutating methods based on the | ||
| /// mutating variants. | ||
| public protocol Numeric : AdditiveArithmetic, ExpressibleByIntegerLiteral { | ||
| /// Creates a new instance from the given integer, if it can be represented | ||
| /// exactly. | ||
| /// | ||
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@@ -100,65 +179,6 @@ public protocol Numeric : Equatable, ExpressibleByIntegerLiteral { | |
| /// instead of the `magnitude` property is encouraged. | ||
| var magnitude: Magnitude { get } | ||
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| /// Multiplies two values and produces their product. | ||
| /// | ||
| /// The multiplication operator (`*`) calculates the product of its two | ||
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@@ -327,7 +347,7 @@ public func abs<T : SignedNumeric & Comparable>(_ x: T) -> T { | |
| return x < (0 as T) ? -x : x | ||
| } | ||
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| extension AdditiveArithmetic { | ||
| /// Returns the given number unchanged. | ||
| /// | ||
| /// You can use the unary plus operator (`+`) to provide symmetry in your | ||
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Can we expand this comment with a note that
zerois the name of the additive identity? Something like/// zero is the identity element for addition; for any value x,
x + .zero == xand.zero + x == x.There was a problem hiding this comment.
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Done. There's still no doc comment on the protocol itself, but writing good doc comments would take time :) I added
TODO's for that.