mat: add VecDense and RawVectorer cases to untransposeExtract (#1186)

* mat: add VecDense.SetRawVector
* mat: add VecDense and RawVectorer cases to untransposeExtract
* mat: add comments to VecDense.{RawVector,SetRawVector}

mat/matrix.go

@@ -244,7 +244,7 @@ func untranspose(a Matrix) (Matrix, bool) {
 func untransposeExtract(a Matrix) (Matrix, bool) {
 	ut, trans := untranspose(a)
 	switch m := ut.(type) {
-	case *DiagDense, *SymBandDense, *TriBandDense, *BandDense, *TriDense, *SymDense, *Dense:
+	case *DiagDense, *SymBandDense, *TriBandDense, *BandDense, *TriDense, *SymDense, *Dense, *VecDense:
 		return m, trans
 	// TODO(btracey): Add here if we ever have an equivalent of RawDiagDense.
 	case RawSymBander:
@@ -287,6 +287,10 @@ func untransposeExtract(a Matrix) (Matrix, bool) {
 		var d Dense
 		d.SetRawMatrix(m.RawMatrix())
 		return &d, trans
+	case RawVectorer:
+		var v VecDense
+		v.SetRawVector(m.RawVector())
+		return &v, trans
 	default:
 		return ut, trans
 	}

mat/vector.go

@@ -215,10 +215,20 @@ func VecDenseCopyOf(a Vector) *VecDense {
 	return v
 }
 
+// RawVector returns the underlying blas64.Vector used by the receiver.
+// Changes to elements in the receiver following the call will be reflected
+// in returned blas64.Vector.
 func (v *VecDense) RawVector() blas64.Vector {
 	return v.mat
 }
 
+// SetRawVector sets the underlying blas64.Vector used by the receiver.
+// Changes to elements in the receiver following the call will be reflected
+// in the input.
+func (v *VecDense) SetRawVector(a blas64.Vector) {
+	v.mat = a
+}
+
 // CopyVec makes a copy of elements of a into the receiver. It is similar to the
 // built-in copy; it copies as much as the overlap between the two vectors and
 // returns the number of elements it copied.