1 files changed, 134 insertions, 0 deletions
diff --git a/usr/dsymonds/iterable/iterable.go b/usr/dsymonds/iterable/iterable.go
new file mode 100644
index 000000000..bdcce11d0
--- /dev/null
+++ b/usr/dsymonds/iterable/iterable.go
@@ -0,0 +1,134 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// The iterable package provides several traversal and searching methods.
+// It can be used on anything that satisfies the Iterable interface,
+// including vector, though certain functions, such as Map, can also be used on
+// something that would produce an infinite amount of data.
+package iterable
+
+import "container/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(interface {}) bool) bool {
+	for e := range iter.Iter() {
+		if !f(e) {
+			return false
+		}
+	}
+	return true
+}
+
+// Any tests whether f is true for at least one element of iter.
+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);
+	for e := range iter.Iter() {
+		vec.Push(e)
+	}
+	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
+}
+
+// Injector is a type representing a function that takes two arguments,
+// an accumulated value and an element, and returns the next accumulated value.
+// See the Inject function.
+type Injector func(interface {}, interface {}) interface{};
+
+// Inject combines the elements of iter by repeatedly calling f with an
+// accumulated value and each element in order. The starting accumulated value
+// is initial, and after each call the accumulated value is set to the return
+// value of f. For instance, to compute a sum:
+//   var arr IntArray = []int{ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
+//   sum := iterable.Inject(arr, 0,
+//                          func(ax interface {}, x interface {}) interface {} {
+//                            return ax.(int) + x.(int) }).(int)
+func Inject(iter Iterable, initial interface {}, f Injector) interface {} {
+	acc := initial;
+	for e := range iter.Iter() {
+		acc = f(acc, e)
+	}
+	return acc
+}
+
+// mappedIterable is a helper struct that implements Iterable, returned by Map.
+type mappedIterable struct {
+	it Iterable;
+	f func(interface {}) 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 {} {
+	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(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:
+// - Zip