From 0eb6df27dc041eafe70befbcb77136a898beb53c Mon Sep 17 00:00:00 2001
From: Ruben Dashyan <ruben.dashyan@numworks.com>
Date: Wed, 19 Feb 2020 12:20:49 +0100
Subject: [PATCH] [poincare] Turn Unit::Dimension::Vector type into a struct

---
 poincare/include/poincare/unit.h | 18 +++++++++-
 poincare/src/multiplication.cpp  | 56 +++++---------------------------
 2 files changed, 26 insertions(+), 48 deletions(-)

diff --git a/poincare/include/poincare/unit.h b/poincare/include/poincare/unit.h
index 486ab91df..c6ee3f61d 100644
--- a/poincare/include/poincare/unit.h
+++ b/poincare/include/poincare/unit.h
@@ -84,7 +84,23 @@ public:
   class Dimension {
   public:
     template<typename T>
-    using Vector = T[NumberOfBaseUnits];
+    struct Vector {
+      const T coefficientAtIndex(size_t i) const {
+        assert(i < NumberOfBaseUnits);
+        return *(reinterpret_cast<const T*>(this) + i);
+      }
+      void setCoefficientAtIndex(size_t i, T c) {
+        assert(i < NumberOfBaseUnits);
+        *(reinterpret_cast<T*>(this) + i) = c;
+      }
+      T time;
+      T distance;
+      T mass;
+      T current;
+      T temperature;
+      T amountOfSubstance;
+      T luminuousIntensity;
+    };
     template <size_t N>
     constexpr Dimension(const Representative (&representatives)[N], const Prefix * stdRepresentativePrefix) :
       m_representatives(representatives),
diff --git a/poincare/src/multiplication.cpp b/poincare/src/multiplication.cpp
index 6292243cc..656544c9a 100644
--- a/poincare/src/multiplication.cpp
+++ b/poincare/src/multiplication.cpp
@@ -302,16 +302,10 @@ Expression Multiplication::shallowReduce(ExpressionNode::ReductionContext reduct
   return privateShallowReduce(reductionContext, true, true);
 }
 
-static void ExponentsCopy(Unit::Dimension::Vector<Integer> &dst, const Unit::Dimension::Vector<Integer> &src) {
-  for (size_t i = 0; i < Unit::NumberOfBaseUnits; i++) {
-    dst[i] = src[i];
-  }
-}
-
 static void ExponentsMetrics(const Unit::Dimension::Vector<Integer> &exponents, size_t & supportSize, Integer & norm) {
   assert(supportSize == 0 && norm.isZero());
   for (size_t i = 0; i < Unit::NumberOfBaseUnits; i++) {
-    Integer unsignedExponent = exponents[i];
+    Integer unsignedExponent = exponents.coefficientAtIndex(i);
     unsignedExponent.setNegative(false);
     if (!unsignedExponent.isZero()) {
       supportSize++;
@@ -347,7 +341,7 @@ static void ExponentsOfBaseUnits(const Expression units, Unit::Dimension::Vector
     // Fill the exponents array with the unit's exponent
     const int indexInTable = static_cast<Unit &>(factor).dimension() - Unit::DimensionTable;
     assert(0 <= indexInTable && indexInTable < Unit::NumberOfBaseUnits);
-    exponents[indexInTable] = exponent;
+    exponents.setCoefficientAtIndex(indexInTable, exponent);
   }
 }
 
@@ -359,17 +353,9 @@ static bool CanSimplifyUnitProduct(
    * 'unitsExponents' Integer array), by applying a given operation. If the
    * result of the operation is simpler, 'bestUnit' and
    * 'bestRemainder' are updated accordingly. */
-  Unit::Dimension::Vector<Integer> simplifiedExponents = {
-    Integer(0),
-    Integer(0),
-    Integer(0),
-    Integer(0),
-    Integer(0),
-    Integer(0),
-    Integer(0),
-  };
+  Unit::Dimension::Vector<Integer> simplifiedExponents;
   for (size_t i = 0; i < Unit::NumberOfBaseUnits; i++) {
-    simplifiedExponents[i] = operationOnExponents(unitsExponents[i], entryUnitExponents[i]);
+    simplifiedExponents.setCoefficientAtIndex(i, operationOnExponents(unitsExponents.coefficientAtIndex(i), entryUnitExponents.coefficientAtIndex(i)));
   }
   size_t simplifiedSupportSize = 0;
   Integer simplifiedNorm(0);
@@ -380,7 +366,7 @@ static bool CanSimplifyUnitProduct(
   if (isSimpler) {
     bestUnit = entryUnit;
     bestUnitNorm = entryUnitNorm;
-    ExponentsCopy(bestRemainderExponents, simplifiedExponents);
+    bestRemainderExponents = simplifiedExponents;
     bestRemainderSupportSize = simplifiedSupportSize;
     bestRemainderNorm = simplifiedNorm;
   }
@@ -418,28 +404,12 @@ Expression Multiplication::shallowBeautify(ExpressionNode::ReductionContext redu
      * - Repeat those steps until no more simplification is possible.
      */
     Multiplication unitsAccu = Multiplication::Builder();
-    Unit::Dimension::Vector<Integer> unitsExponents = {
-      Integer(0),
-      Integer(0),
-      Integer(0),
-      Integer(0),
-      Integer(0),
-      Integer(0),
-      Integer(0),
-    };
+    Unit::Dimension::Vector<Integer> unitsExponents;
     ExponentsOfBaseUnits(units, unitsExponents);
     size_t unitsSupportSize = 0;
     Integer unitsNorm(0);
     ExponentsMetrics(unitsExponents, unitsSupportSize, unitsNorm);
-    Unit::Dimension::Vector<Integer> bestRemainderExponents = {
-      Integer(0),
-      Integer(0),
-      Integer(0),
-      Integer(0),
-      Integer(0),
-      Integer(0),
-      Integer(0),
-    };
+    Unit::Dimension::Vector<Integer> bestRemainderExponents;
     while (unitsSupportSize > 1) {
       Expression bestUnit;
       Integer bestUnitNorm(0);
@@ -447,15 +417,7 @@ Expression Multiplication::shallowBeautify(ExpressionNode::ReductionContext redu
       Integer bestRemainderNorm = unitsNorm;
       for (const Unit::Dimension * dim = Unit::DimensionTable + Unit::NumberOfBaseUnits; dim < Unit::DimensionTableUpperBound; dim++) {
         Unit entryUnit = Unit::Builder(dim, dim->stdRepresentative(), dim->stdRepresentativePrefix());
-        Unit::Dimension::Vector<Integer> entryUnitExponents = {
-          Integer(0),
-          Integer(0),
-          Integer(0),
-          Integer(0),
-          Integer(0),
-          Integer(0),
-          Integer(0),
-        };
+        Unit::Dimension::Vector<Integer> entryUnitExponents;
         Integer entryUnitNorm(0);
         size_t entryUnitSupportSize = 0;
         ExponentsOfBaseUnits(entryUnit.clone().shallowReduce(reductionContext), entryUnitExponents);
@@ -477,7 +439,7 @@ Expression Multiplication::shallowBeautify(ExpressionNode::ReductionContext redu
       }
       const int position = unitsAccu.numberOfChildren();
       unitsAccu.addChildAtIndexInPlace(bestUnit, position, position);
-      ExponentsCopy(unitsExponents, bestRemainderExponents);
+      unitsExponents = bestRemainderExponents;
       unitsSupportSize = bestRemainderSupportSize;
       unitsNorm = bestRemainderNorm;
     }