[stdlib] Add a negation for 'VectorProtocol' when scalar is signed (#25494)

rxwei · web-flow · commit 5ce378a19ef6 · 2019-06-14T21:33:23.000-07:00
diff --git a/stdlib/public/core/AutoDiff.swift b/stdlib/public/core/AutoDiff.swift
@@ -51,6 +51,12 @@ public extension VectorProtocol {
   }
 }
 
+public extension VectorProtocol where VectorSpaceScalar: SignedNumeric {
+  static prefix func - (x: Self) -> Self {
+    .zero - x
+  }
+}
+
 /// A type that mathematically represents a differentiable manifold whose
 /// tangent spaces are finite-dimensional.
 public protocol Differentiable {

Original file line number	Diff line number	Diff line change
`@@ -51,6 +51,12 @@ public extension VectorProtocol {`
`51`	`51`	`}`
`52`	`52`	`}`
`53`	`53`
	`54`	`+public extension VectorProtocol where VectorSpaceScalar: SignedNumeric {`
	`55`	`+ static prefix func - (x: Self) -> Self {`
	`56`	`+ .zero - x`
	`57`	`+ }`
	`58`	`+}`
	`59`	`+`
`54`	`60`	`/// A type that mathematically represents a differentiable manifold whose`
`55`	`61`	`/// tangent spaces are finite-dimensional.`
`56`	`62`	`public protocol Differentiable {`