Sk2x/Sk4x: add negate(), operator -()

src/core/Sk2x.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef Sk2x_DEFINED
 #define Sk2x_DEFINED
 
@@ skipping 40 matching lines @@
     Sk2x multiply(const Sk2x&) const;
 
     Sk2x operator +(const Sk2x& o) const { return this->add(o); }
     Sk2x operator -(const Sk2x& o) const { return this->subtract(o); }
     Sk2x operator *(const Sk2x& o) const { return this->multiply(o); }
 
     Sk2x& operator +=(const Sk2x& o) { return (*this = *this + o); }
     Sk2x& operator -=(const Sk2x& o) { return (*this = *this - o); }
     Sk2x& operator *=(const Sk2x& o) { return (*this = *this * o); }
 
+    Sk2x negate() const { return Sk2x(0) - *this; }
+    Sk2x operator -() const { return this->negate(); }
+
     Sk2x rsqrt() const;   // Approximate 1/this->sqrt().
     Sk2x  sqrt() const;   // this->multiply(this->rsqrt()) may be faster, but less precise.
 
     static Sk2x Min(const Sk2x&, const Sk2x&);
     static Sk2x Max(const Sk2x&, const Sk2x&);
 
 private:
 #define SK2X_PRIVATE 1
     #if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2 && !defined(SKNX_NO_SIMD)
         #include "../opts/Sk2x_sse.h"
     #elif defined(__ARM_NEON__)                   && !defined(SKNX_NO_SIMD)
         #include "../opts/Sk2x_neon.h"
     #else
         #include "../opts/Sk2x_none.h"
     #endif
 #undef SK2X_PRIVATE
 };
 
 #if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2 && !defined(SKNX_NO_SIMD)
     #include "../opts/Sk2x_sse.h"
 #elif defined(__ARM_NEON__)                   && !defined(SKNX_NO_SIMD)
     #include "../opts/Sk2x_neon.h"
 #else
     #include "../opts/Sk2x_none.h"
 #endif
 
 #endif//Sk2x_DEFINED