1 files changed, 49 insertions, 15 deletions

diff --git a/src/lib/container/iterable.go b/src/lib/container/iterable.go
index 7963d14b5..a4a0d4c0f 100644
--- a/src/lib/container/iterable.go
+++ b/src/lib/container/iterable.go
@@ -10,15 +10,17 @@ package iterable
 
 import "vector"
 
-
 type Iterable interface {
 	// Iter should return a fresh channel each time it is called.
 	Iter() <-chan interface {}
 }
 
+func not(f func(interface {}) bool) (func(interface {}) bool) {
+  return func(e interface {}) bool { return !f(e) }
+}
 
 // All tests whether f is true for every element of iter.
-func All(iter Iterable, f func(e interface {}) bool) bool {
+func All(iter Iterable, f func(interface {}) bool) bool {
 	for e := range iter.Iter() {
 		if !f(e) {
 			return false
@@ -27,13 +29,11 @@ func All(iter Iterable, f func(e interface {}) bool) bool {
 	return true
 }
 
-
 // Any tests whether f is true for at least one element of iter.
-func Any(iter Iterable, f func(e interface {}) bool) bool {
-	return !All(iter, func(e interface {}) bool { return !f(e) });
+func Any(iter Iterable, f func(interface {}) bool) bool {
+	return !All(iter, not(f))
 }
 
-
 // Data returns a slice containing the elements of iter.
 func Data(iter Iterable) []interface {} {
 	vec := vector.New(0);
@@ -43,6 +43,41 @@ func Data(iter Iterable) []interface {} {
 	return vec.Data()
 }
 
+// filteredIterable is a struct that implements Iterable with each element
+// passed through a filter.
+type filteredIterable struct {
+	it Iterable;
+	f func(interface {}) bool;
+}
+
+func (f *filteredIterable) iterate(out chan<- interface {}) {
+	for e := range f.it.Iter() {
+		if f.f(e) {
+			out <- e
+		}
+	}
+	close(out)
+}
+
+func (f *filteredIterable) Iter() <-chan interface {} {
+	ch := make(chan interface {});
+	go f.iterate(ch);
+	return ch;
+}
+
+// Filter returns an Iterable that returns the elements of iter that satisfy f.
+func Filter(iter Iterable, f func(interface {}) bool) Iterable {
+	return &filteredIterable{ iter, f }
+}
+
+// Find returns the first element of iter that satisfies f.
+// Returns nil if no such element is found.
+func Find(iter Iterable, f func(interface {}) bool) interface {} {
+	for e := range Filter(iter, f).Iter() {
+		return e
+	}
+	return nil
+}
 
 // mappedIterable is a helper struct that implements Iterable, returned by Map.
 type mappedIterable struct {
@@ -50,31 +85,30 @@ type mappedIterable struct {
 	f func(interface {}) interface {};
 }
 
-
-func (m mappedIterable) iterate(out chan<- interface {}) {
+func (m *mappedIterable) iterate(out chan<- interface {}) {
 	for e := range m.it.Iter() {
 		out <- m.f(e)
 	}
 	close(out)
 }
 
-
-func (m mappedIterable) Iter() <-chan interface {} {
+func (m *mappedIterable) Iter() <-chan interface {} {
 	ch := make(chan interface {});
 	go m.iterate(ch);
 	return ch;
 }
 
-
 // Map returns an Iterable that returns the result of applying f to each
 // element of iter.
-func Map(iter Iterable, f func(e interface {}) interface {}) Iterable {
-	return mappedIterable{ iter, f }
+func Map(iter Iterable, f func(interface {}) interface {}) Iterable {
+	return &mappedIterable{ iter, f }
 }
 
+// Partition(iter, f) returns Filter(iter, f) and Filter(iter, !f).
+func Partition(iter Iterable, f func(interface {}) bool) (Iterable, Iterable)  {
+  return Filter(iter, f), Filter(iter, not(f))
+}
 
 // TODO:
-// - Find, Filter
 // - Inject
-// - Partition
 // - Zip