map is a reference type

4 files changed, 56 insertions, 52 deletions

diff --git a/skate/schema.go b/skate/schema.go
index 14397e9..a9570b7 100644
--- a/skate/schema.go
+++ b/skate/schema.go
@@ -80,7 +80,7 @@ func parseIsbn(s string) []string {
 		u            []rune
 		z            string
 	)
-	valid := setPool.Get().(*set.Set)
+	valid := setPool.Get().(set.Set)
 	valid.Clear()
 	defer setPool.Put(valid)
 	for _, v := range append(candidates10, candidates13...) {
diff --git a/skate/set/set.go b/skate/set/set.go
index 6bad47e..29cd3ef 100644
--- a/skate/set/set.go
+++ b/skate/set/set.go
@@ -8,31 +8,47 @@ import (
 // Set implements basic string set operations, not thread-safe.
 type Set map[string]struct{}
 
-func (s *Set) Clear() {
-	for k := range *s {
-		delete(*s, k)
+// New creates a new set.
+func New() Set {
+	var s = make(Set)
+	return s
+}
+
+// FromSlice initializes a set from a slice.
+func FromSlice(vs []string) Set {
+	s := New()
+	for _, v := range vs {
+		s.Add(v)
+	}
+	return s
+}
+
+// Clear removes all elements.
+func (s Set) Clear() {
+	for k := range s {
+		delete(s, k)
 	}
 }
 
 // Add adds an element.
-func (s *Set) Add(v string) *Set {
-	(*s)[v] = struct{}{}
+func (s Set) Add(v string) Set {
+	s[v] = struct{}{}
 	return s
 }
 
 // Len returns number of elements in set.
-func (s *Set) Len() int {
-	return len(*s)
+func (s Set) Len() int {
+	return len(s)
 }
 
 // IsEmpty returns if set has zero elements.
-func (s *Set) IsEmpty() bool {
+func (s Set) IsEmpty() bool {
 	return s.Len() == 0
 }
 
 // Equals returns true, if sets contain the same elements.
-func (s *Set) Equals(t *Set) bool {
-	for k := range *s {
+func (s Set) Equals(t Set) bool {
+	for k := range s {
 		if !t.Contains(k) {
 			return false
 		}
@@ -41,13 +57,13 @@ func (s *Set) Equals(t *Set) bool {
 }
 
 // Contains returns membership status.
-func (s *Set) Contains(v string) bool {
-	_, ok := (*s)[v]
+func (s Set) Contains(v string) bool {
+	_, ok := (s)[v]
 	return ok
 }
 
 // Intersection returns a new set containing all elements found in both sets.
-func (s *Set) Intersection(t *Set) *Set {
+func (s Set) Intersection(t Set) Set {
 	u := New()
 	for _, v := range s.Slice() {
 		if t.Contains(v) {
@@ -58,7 +74,7 @@ func (s *Set) Intersection(t *Set) *Set {
 }
 
 // Union returns the union of two sets.
-func (s *Set) Union(t *Set) *Set {
+func (s Set) Union(t Set) Set {
 	u := New()
 	for _, v := range s.Slice() {
 		u.Add(v)
@@ -70,16 +86,16 @@ func (s *Set) Union(t *Set) *Set {
 }
 
 // Slice returns all elements as a slice.
-func (s *Set) Slice() (result []string) {
-	for k := range *s {
+func (s Set) Slice() (result []string) {
+	for k := range s {
 		result = append(result, k)
 	}
 	return
 }
 
-// SortedSlice returns all elements as a slice, sorted.
-func (s *Set) SortedSlice() (result []string) {
-	for k := range *s {
+// Sorted returns all elements as a slice, sorted.
+func (s Set) Sorted() (result []string) {
+	for k := range s {
 		result = append(result, k)
 	}
 	sort.Strings(result)
@@ -87,9 +103,9 @@ func (s *Set) SortedSlice() (result []string) {
 }
 
 // TopK returns at most k elements.
-func (s *Set) TopK(k int) *Set {
+func (s Set) TopK(k int) Set {
 	var top []string
-	for i, v := range s.SortedSlice() {
+	for i, v := range s.Sorted() {
 		if i < k {
 			top = append(top, v)
 		}
@@ -97,9 +113,10 @@ func (s *Set) TopK(k int) *Set {
 	return FromSlice(top)
 }
 
-func (s *Set) Product(t *Set) (result [][]string) {
-	for k := range *s {
-		for l := range *t {
+// Product returns a slice of pairs, representing the cartesian product.
+func (s Set) Product(t Set) (result [][]string) {
+	for k := range s {
+		for l := range t {
 			result = append(result, []string{k, l})
 		}
 	}
@@ -107,7 +124,7 @@ func (s *Set) Product(t *Set) (result [][]string) {
 }
 
 // Jaccard returns the jaccard index of sets s and t.
-func (s *Set) Jaccard(t *Set) float64 {
+func (s Set) Jaccard(t Set) float64 {
 	if s.IsEmpty() && t.IsEmpty() {
 		return 1
 	}
@@ -118,12 +135,13 @@ func (s *Set) Jaccard(t *Set) float64 {
 	}
 }
 
-func (s *Set) Join(sep string) string {
+// Join joins elements from a set with given separator.
+func (s Set) Join(sep string) string {
 	return strings.Join(s.Slice(), sep)
 }
 
 // Max returns the size of the largest set.
-func Max(ss ...*Set) (max int) {
+func Max(ss ...Set) (max int) {
 	for _, s := range ss {
 		if s.Len() > max {
 			max = s.Len()
@@ -133,7 +151,7 @@ func Max(ss ...*Set) (max int) {
 }
 
 // Min returns the size of the smallest set.
-func Min(ss ...*Set) (min int) {
+func Min(ss ...Set) (min int) {
 	min = 2 << 30
 	for _, s := range ss {
 		if s.Len() < min {
@@ -143,27 +161,13 @@ func Min(ss ...*Set) (min int) {
 	return
 }
 
-func Filter(s *Set, f func(string) bool) *Set {
+// Filter returns a set containing all elements, which satisfy a given predicate.
+func Filter(s Set, f func(string) bool) Set {
 	t := New()
-	for v := range *s {
+	for v := range s {
 		if f(v) {
 			t.Add(v)
 		}
 	}
 	return t
 }
-
-// New creates a new set.
-func New() *Set {
-	s := make(Set)
-	return &s
-}
-
-// FromSlice initializes a set from a slice.
-func FromSlice(vs []string) *Set {
-	s := New()
-	for _, v := range vs {
-		s.Add(v)
-	}
-	return s
-}
diff --git a/skate/set/set_test.go b/skate/set/set_test.go
index 403b6df..dffb3e3 100644
--- a/skate/set/set_test.go
+++ b/skate/set/set_test.go
@@ -22,9 +22,9 @@ func TestSet(t *testing.T) {
 
 	r := make(Set)
 	r.Add("2")
-	is.True(s.Intersection(&r).IsEmpty())
-	is.Equal(s.Union(&r).Len(), 2)
-	is.Equal(s.Union(&r).SortedSlice(), []string{"1", "2"})
+	is.True(s.Intersection(r).IsEmpty())
+	is.Equal(s.Union(r).Len(), 2)
+	is.Equal(s.Union(r).Sorted(), []string{"1", "2"})
 
 	r.Add("3")
 	r.Add("4")
@@ -35,7 +35,7 @@ func TestSet(t *testing.T) {
 	top := make(Set)
 	top.Add("2")
 	top.Add("3")
-	is.Equal(r.TopK(2), &top)
+	is.Equal(r.TopK(2), top)
 
 	r.Clear()
 	is.Equal(r.Len(), 0)
diff --git a/skate/verify.go b/skate/verify.go
index 914f6a4..e6ab03e 100644
--- a/skate/verify.go
+++ b/skate/verify.go
@@ -505,7 +505,7 @@ func VerifyMinTitleLength(a, b *Release, minTitleLength int) MatchResult {
 		return MatchResult{StatusStrong, ReasonVersionedDOI}
 	}
 	if len(a.Extra.DataCite.Relations) > 0 || len(b.Extra.DataCite.Relations) > 0 {
-		getRelatedDOI := func(rel *Release) *set.Set {
+		getRelatedDOI := func(rel *Release) set.Set {
 			ss := set.New()
 			for _, rel := range rel.Extra.DataCite.Relations {
 				if strings.ToLower(rel.RelatedIdentifierType) != "doi" {
@@ -737,7 +737,7 @@ func parsePageString(s string) *ParsedPages {
 // averageScore take a limited set of authors and calculates pairwise
 // similarity scores, then returns the average of the best scores; between 0
 // and 1.
-func averageScore(a, b *set.Set) float64 {
+func averageScore(a, b set.Set) float64 {
 	aTrimmed := a.TopK(5)
 	bTrimmed := b.TopK(5)
 	maxScores := make(map[string]float64) // For each a, keep the max.