First complete version

functional.go

@@ -0,0 +1,219 @@
+package FunctionalLib
+
+import Seq "github.com/geniussportsgroup/Slist"
+
+type SequentialIterator interface {
+	ResetFirst() interface{}
+	HasCurr() bool
+	GetCurr() interface{}
+	Next() interface{}
+}
+
+type Sequence interface {
+	Traverse(func(interface{}) bool) bool
+	Append(item interface{}, items ...interface{}) interface{}
+	Size() int
+	Swap(other interface{}) interface{}
+	IsEmpty() bool
+	CreateIterator() interface{}
+}
+
+// Execute operation receiving every item of the sequence. Return seq
+func ForEach(seq Sequence, operation func(interface{})) interface{} {
+
+	seq.Traverse(func(i interface{}) bool {
+
+		operation(i)
+		return true
+	})
+
+	return seq
+}
+
+// Return true if all the elements of the sequence meets predicate
+func All(seq Sequence, predicate func(interface{}) bool) bool {
+
+	return seq.Traverse(predicate)
+}
+
+func Exist(seq Sequence, predicate func(interface{}) bool) bool {
+
+	return !All(seq, func(i interface{}) bool {
+		return !predicate(i)
+	})
+}
+
+// Return a new seq with the items of sequence transformed with transformation operation
+func Map(seq Sequence, transformation func(interface{}) interface{}) *Seq.Slist {
+
+	ret := Seq.New()
+	ForEach(seq, func(item interface{}) {
+		ret.Append(transformation(item))
+	})
+	return ret
+}
+
+// Return a new seq with the items of sequence transformed with transformation operation for the items
+// satisfying the predicate
+func MapIf(seq Sequence,
+	transformation func(interface{}) interface{},
+	predicate func(interface{}) bool) *Seq.Slist {
+
+	ret := Seq.New()
+	ForEach(seq, func(item interface{}) {
+		if predicate(item) {
+			ret.Append(transformation(item))
+		}
+	})
+	return ret
+}
+
+// Return a list containing the items satisfying predicate
+func Filter(seq Sequence, predicate func(interface{}) bool) *Seq.Slist {
+
+	ret := Seq.New()
+	ForEach(seq, func(item interface{}) {
+		if predicate(item) {
+			ret.Append(item)
+		}
+	})
+	return ret
+}
+
+type Pair struct {
+	item1, item2 interface{}
+}
+
+// Zip two lists into one list of pair. The result is truncated to the shortest list
+func Zip(s1, s2 Sequence) *Seq.Slist {
+
+	ret := Seq.New()
+
+	it1, it2 := s1.CreateIterator().(SequentialIterator), s2.CreateIterator().(SequentialIterator)
+	for it1.HasCurr() && it2.HasCurr() {
+
+		ret.Append(Pair{
+			item1: it1.GetCurr(),
+			item2: it2.GetCurr(),
+		})
+
+		it1.Next()
+		it2.Next()
+	}
+
+	return ret
+}
+
+// Unzip a list of pairs into two separated lists
+func Unzip(seq *Seq.Slist) (*Seq.Slist, *Seq.Slist) {
+
+	l1 := Seq.New()
+	l2 := Seq.New()
+
+	for it := seq.CreateIterator().(*Seq.Iterator); it.HasCurr(); it.Next() {
+
+		curr := it.GetCurr().(Pair)
+		l1.Append(curr.item1)
+		l2.Append(curr.item2)
+	}
+
+	return l1, l2
+}
+
+// Split seq into two lists. First contains items satisfying predicate and the second the complement
+func Split(seq Sequence, predicate func(item interface{}) bool) (*Seq.Slist, *Seq.Slist) {
+
+	l1 := Seq.New()
+	l2 := Seq.New()
+
+	ForEach(seq, func(i interface{}) {
+		if predicate(i) {
+			l1.Append(i)
+		} else {
+			l2.Append(i)
+		}
+	})
+
+	return l1, l2
+}
+
+// Return the first item in seq satisfying predicate. If not item is found, the it returns nil
+func Find(seq Sequence, predicate func(item interface{}) bool) interface{} {
+
+	for it := seq.CreateIterator().(SequentialIterator); it.HasCurr(); it.Next() {
+		item := it.GetCurr()
+		if predicate(item) {
+			return item
+		}
+	}
+	return nil
+}
+
+// Return a sequence containing the first n items from the sequence
+func Take(seq Sequence, n int) *Seq.Slist {
+
+	ret := Seq.New()
+	for it := seq.CreateIterator().(SequentialIterator); it.HasCurr() && n > 0; it.Next() {
+		ret.Append(it.GetCurr())
+		n--
+	}
+
+	return ret
+}
+
+// Return a sequence containing the items after the first n from the sequence
+func Drop(seq Sequence, n int) *Seq.Slist {
+
+	ret := Seq.New()
+	for i, it := 0, seq.CreateIterator().(SequentialIterator); it.HasCurr(); it.Next() {
+		if i < n {
+			i++
+			continue
+		}
+		ret.Append(it.GetCurr())
+	}
+
+	return ret
+}
+
+// Return f(in, ..., f(i2, f(i1, initVal) ... ))
+func Foldl(seq Sequence, initVal interface{},
+	f func(acu, item interface{}) interface{}) interface{} {
+
+	retVal := initVal
+	ForEach(seq, func(i interface{}) {
+		retVal = f(retVal, i)
+	})
+	return retVal
+}
+
+// Return the n-th item in the sequence. Return nil if n is negative o greater than seq.Size()
+func Nth(seq Sequence, n int) interface{} {
+
+	if n < 0 || n >= seq.Size() {
+		return nil
+	}
+
+	for it := seq.CreateIterator().(SequentialIterator); it.HasCurr(); it.Next() {
+		if n == 0 {
+			return it.GetCurr()
+		}
+		n--
+	}
+
+	return nil // it should not be reached!
+}
+
+// Return the position in the sequence of the first element satisfying predicate. If no element satisfies
+// predicate then it returns -1
+func Position(seq Sequence, predicate func(item interface{}) bool) int {
+
+	for pos, it := 0, seq.CreateIterator().(SequentialIterator); it.HasCurr(); it.Next() {
+		if predicate(it.GetCurr()) {
+			return pos
+		}
+		pos++
+	}
+
+	return -1
+}