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ops_set_rank.go
77 lines (68 loc) · 1.67 KB
/
ops_set_rank.go
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package rel
import (
"sort"
)
// Rank ...
func Rank(s Set, rankerf func(v Tuple) (Tuple, error)) (Set, error) {
if !s.IsTrue() {
return None, nil
}
entries := []rankerEntry{}
for e := s.Enumerator(); e.MoveNext(); {
input := e.Current().(Tuple)
rankers, err := rankerf(input)
if err != nil {
return nil, err
}
entries = append(entries, rankerEntry{input, rankers})
}
ranker := newRanker(entries)
for _, attr := range entries[0].ranker.Names().Names() {
ranker.attr = attr
sort.Sort(ranker)
current := ranker.entries[0].ranker.MustGet(attr)
rank := 0
for i, r := range ranker.entries {
a := r.ranker.MustGet(attr)
if !a.Equal(current) {
rank = i
current = a
}
r.input = r.input.With(attr, NewNumber(float64(rank)))
}
}
values := make([]Value, 0, len(entries))
for _, entry := range entries {
values = append(values, entry.input)
}
return NewSet(values...), nil
}
type rankerEntry struct {
input, ranker Tuple
}
type rankerSlice struct {
entries []*rankerEntry
attr string
}
func newRanker(entries []rankerEntry) rankerSlice {
var r rankerSlice
for i := range entries {
r.entries = append(r.entries, &entries[i])
}
return r
}
// Len is the number of elements in the collection.
func (o rankerSlice) Len() int {
return len(o.entries)
}
// Less reports whether the element with
// index i should sort before the element with index j.
func (o rankerSlice) Less(i, j int) bool {
a := o.entries[i].ranker.MustGet(o.attr)
b := o.entries[j].ranker.MustGet(o.attr)
return a.Less(b)
}
// Swap swaps the elements with indexes i and j.
func (o rankerSlice) Swap(i, j int) {
o.entries[i], o.entries[j] = o.entries[j], o.entries[i]
}