rename goutils to obiutils

Former-commit-id: 2147f53db972bba571dfdae30c51b62d3e69cec5

pkg/obiutils/ranks.go

@@ -0,0 +1,86 @@
+package obiutils
+
+import (
+	"sort"
+)
+
+// intRanker is a helper type for the rank function.
+type intRanker struct {
+	x []int // Data to be ranked.
+	r []int // A list of indexes into f that reflects rank order after sorting.
+}
+
+// ranker satisfies the sort.Interface without mutating the reference slice, f.
+func (r intRanker) Len() int           { return len(r.x) }
+func (r intRanker) Less(i, j int) bool { return r.x[r.r[i]] < r.x[r.r[j]] }
+func (r intRanker) Swap(i, j int)      { r.r[i], r.r[j] = r.r[j], r.r[i] }
+
+func IntOrder(data []int) []int {
+	if len(data) == 0 {
+		return nil
+	}
+
+	r := make([]int, len(data))
+	rk := intRanker{
+		x: data,
+		r: r,
+	}
+
+	for i := 0; i < len(data); i++ {
+		rk.r[i] = i
+	}
+
+	sort.Sort(rk)
+
+	return r
+}
+
+func ReverseIntOrder(data []int) []int {
+	if len(data) == 0 {
+		return nil
+	}
+
+	r := make([]int, len(data))
+	rk := intRanker{
+		x: data,
+		r: r,
+	}
+
+	for i := 0; i < len(data); i++ {
+		rk.r[i] = i
+	}
+
+	sort.Sort(sort.Reverse(rk))
+
+	return r
+}
+
+type Ranker[T sort.Interface] struct {
+	x T     // Data to be ranked.
+	r []int // A list of indexes into f that reflects rank order after sorting.
+}
+
+// ranker satisfies the sort.Interface without mutating the reference slice, f.
+func (r Ranker[_]) Len() int           { return len(r.r) }
+func (r Ranker[T]) Less(i, j int) bool { return r.x.Less(r.r[i], r.r[j]) }
+func (r Ranker[_]) Swap(i, j int)      { r.r[i], r.r[j] = r.r[j], r.r[i] }
+
+func Order[T sort.Interface](data T) []int {
+	ldata := data.Len()
+	if ldata == 0 {
+		return nil
+	}
+	r := make([]int, ldata)
+	rk := Ranker[T]{
+		x: data,
+		r: r,
+	}
+
+	for i := 0; i < ldata; i++ {
+		rk.r[i] = i
+	}
+
+	sort.Sort(rk)
+
+	return r
+}