dsp/window: move complex sequence weighting onto Values

This simplifies the API and removes the NaN from Inf problem.

dsp/window/window_parametric.go

@@ -147,23 +147,10 @@ func (v Values) Transform(seq []float64) []float64 {
 	return seq
 }
 
-// ValuesComplex is an arbitrary complex window function.
-type ValuesComplex []complex128
-
-// NewValuesComplex returns a ValuesComplex of length n with weights corresponding
-// to the provided window function.
-func NewValuesComplex(window func([]complex128) []complex128, n int) ValuesComplex {
-	v := make(ValuesComplex, n)
-	for i := range v {
-		v[i] = 1
-	}
-	return window(v)
-}
-
-// Transform applies the weights in the receiver to seq in place, returning the
-// result. If v is nil, Transform is a no-op, otherwise the length of v must
-// match the length of seq.
-func (v ValuesComplex) Transform(seq []complex128) []complex128 {
+// TransformComplex applies the weights in the receiver to seq in place, returning
+// the result. If v is nil, TransformComplex is a no-op, otherwise the length of v
+// must match the length of seq.
+func (v Values) TransformComplex(seq []complex128) []complex128 {
 	if v == nil {
 		return seq
 	}
@@ -171,7 +158,8 @@ func (v ValuesComplex) Transform(seq []complex128) []complex128 {
 		panic("window: length mismatch")
 	}
 	for i, w := range v {
-		seq[i] *= w
+		sv := seq[i]
+		seq[i] = complex(w*real(sv), w*imag(sv))
 	}
 	return seq
 }

dsp/window/window_test.go

@@ -202,7 +202,7 @@ func TestWindowsComplex(t *testing.T) {
 				src[i] = complex(1, 1)
 			}
 
-			dst = NewValuesComplex(test.fnCmplx, len(src)).Transform(src)
+			dst = NewValues(test.fn, len(src)).TransformComplex(src)
 			if !equalApprox(dst, test.want, tol) {
 				t.Errorf("unexpected result for lookup window function %q:\ngot:%#.6v\nwant:%#.6v", test.name, dst, test.want)
 			}