diff --git a/iter/iter.go b/iter/iter.go
index 62fbc0e..e026245 100644
--- a/iter/iter.go
+++ b/iter/iter.go
@@ -80,3 +80,24 @@ func Max[T constraints.Ordered](src Able[T]) T {
 	}
 	return max
 }
+
+// Discarded Iterator types:
+//
+// This was my first attempt. I like to have a method that returns a bool so
+// you can use it succinctly in a for loop, but I didn't love having to call
+// both done and next
+//
+// type Ator[T any] interface {
+// 	Done() bool
+// 	Next() T
+// }
+//
+// I was never optimistic about this. In practice, using this in a for loop is
+// just annoying so I stopped doing it. But also there's another thing I find
+// annoying: it's a copy every time. You're not really iterating over the
+// values, you're iterating over copies of the values, it seemed like a lot of
+// unecessary copying.
+//
+// type Ator[T any] interface {
+//   Next() (T, bool)
+// }
diff --git a/iter/slice.go b/iter/slice.go
new file mode 100644
index 0000000..0ea82b7
--- /dev/null
+++ b/iter/slice.go
@@ -0,0 +1,26 @@
+package iter
+
+import "constraints"
+
+type slice[T any] []T
+
+type sliceIter[T any] struct {
+	s slice[T]
+	i int
+}
+
+func (it *sliceIter[T]) Next(v *T) bool {
+	if it.i >= len(it.s) {
+		return false
+	}
+	*v = it.s[it.i]
+	it.i++
+	return true
+}
+
+func (it *sliceIter[T]) Iter() Ator[T] { return &sliceIter[T]{s: it.s} }
+
+func (s slice[T]) Iter() Ator[T] { return &sliceIter[T]{s: s} }
+
+// Slice takes a slice and returns an iterable backed by that slice
+func Slice[T constraints.Integer](s []T) Able[T] { return slice[T](s) }
diff --git a/list/iter.go b/list/iter.go
index e1749c2..28a0fb6 100644
--- a/list/iter.go
+++ b/list/iter.go
@@ -1,15 +1,15 @@
 package list
 
-type Iterable[T any] interface {
-	Iter() Iter[T]
-}
-
-type Iter[T any] interface {
-	Next(*T) bool
-}
+// type Iterable[T any] interface {
+// 	Iter() Iter[T]
+// }
+//
+// type Iter[T any] interface {
+// 	Next(*T) bool
+// }
 
 // for v, it := iter.Ate(foods); it.Next(&v); {
-// 
+//
 // }
 
 // This actually works, but for some reason I don't yet understand, defining
@@ -20,7 +20,7 @@ type Iter[T any] interface {
 //
 // func Max[T constraints.Ordered](l Iterable[T]) T {
 // 	it := l.Iter()
-// 
+//
 // 	var v T
 // 	if !it.Next(&v) {
 // 		return v
@@ -34,7 +34,6 @@ type Iter[T any] interface {
 // 	return max
 // }
 
-
 // Discarded Iterator types:
 //
 // This was my first attempt. I like to have a method that returns a bool so
diff --git a/list/list.go b/list/list.go
index 4f01bd5..bb99ea4 100644
--- a/list/list.go
+++ b/list/list.go
@@ -5,6 +5,8 @@ import (
 	"sync"
 	"constraints"
 	"fmt"
+
+	"github.com/jordanorelli/generic/iter"
 )
 
 type node[T any] struct {
@@ -41,9 +43,6 @@ func Make[T any](vals ...T) List[T] {
 	return l
 }
 
-// func From[T any](it iter.Able) List[T] {
-// }
-
 // Empty is true for empty lists
 func (l List[T]) Empty() bool {
 	return l.head == nil
@@ -93,7 +92,9 @@ func (l List[T]) Head() T {
 
 // Tail returns a list which is the original list without its Head element.
 // If the original list is an empty list or a list of size 1, Tail is an
-// empty list.
+// empty list. Note that Tail creates a new list that is backed by the same
+// elements as the old list; mutations on the origin list are visible in the
+// tail and vice-versa.
 func (l List[T]) Tail() List[T] {
 	if l.head == nil || l.head.next == nil {
 		return List[T]{}
@@ -114,13 +115,13 @@ func (l List[T]) Len() int {
 	return i
 }
 
-type iter[T any] struct {
+type _iter[T any] struct {
 	n *node[T]
 }
 
-func (i iter[T]) Done() bool { return i.n == nil }
+func (i _iter[T]) Done() bool { return i.n == nil }
 
-func (i *iter[T]) Next(dest *T) bool {
+func (i *_iter[T]) Next(dest *T) bool {
 	if i.n == nil {
 		return false
 	}
@@ -130,9 +131,9 @@ func (i *iter[T]) Next(dest *T) bool {
 	return true
 }
 
-func (l List[T]) Iter() Iter[T] {
-	return &iter[T]{n: l.head}
-}
+func (i *_iter[T]) Iter() iter.Ator[T] { return &_iter[T]{n: i.n} }
+
+func (l List[T]) Iter() iter.Ator[T] { return &_iter[T]{n: l.head} }
 
 func Max[T constraints.Ordered](l List[T]) T {
  	if l.Empty() {
@@ -149,45 +150,81 @@ func Max[T constraints.Ordered](l List[T]) T {
  	return v
 }
 
+// Map exists as a method to permit chaining in the event that your input
+// function maps T -> T. Since methods cannot have type parameters, mapping a
+// function that transforms T -> Z is not possible as a method.
+func (l List[T]) Map(f func(T) T) List[T] { return Map(l, f) }
+
 // Map applies the input function f to each element of the list l, returning a
 // new list containing the values produced by f
-func (l List[T]) Map(f func(T) T) List[T] {
+func Map[T any, Z any](l List[T], f func(T) Z) List[Z] {
 	if l.Empty() {
-		return List[T]{}
+		var empty List[Z]
+		return empty
 	}
 
-	mapped := List[T]{head: &node[T]{val: f(l.head.val)}}
+	mapped := List[Z]{head: &node[Z]{val: f(l.head.val)}}
 	last := mapped.head
 	for n := l.head.next; n != nil; n = n.next {
-		last.next = &node[T]{val: f(n.val)}
+		last.next = &node[Z]{val: f(n.val)}
 		last = last.next
 	}
 
 	return mapped
 }
 
+type numbered[T any] struct {
+	val T
+	i int
+}
+
+func waitNClose[T any](wg *sync.WaitGroup, c chan T) {
+	wg.Wait()
+	close(c)
+}
+
 // Run is the same as Map, but is run concurrently. The function f will be run
-// for every element of l in its own goroutine.
+// for every element of l in its own goroutine. The results of running f on
+// each of the inputs will be stored into a new list in an order-preserving
+// manner.
 func Run[T any, Z any](l List[T], f func(T) Z) List[Z] {
+	if l.Empty() {
+		var empty List[Z]
+		return empty
+	}
+
+	// surprise: type declarations are not allowed inside of generic functions
+	//
+	// type numbered[T any] struct {
+	// 	val T
+	// 	i int
+	// }
+
 	var wg sync.WaitGroup
-	c := make(chan Z)
+	c := make(chan numbered[Z])
 
-	for n := l.head; n != nil; n = n.next {
+	i := 0
+	for n := l.head; n != nil; n = n.next{
 		wg.Add(1)
-		go func(v T) {
+		go func(v T, i int) {
 			defer wg.Done()
-			c <- f(v)
-		}(n.val)
+			c <- numbered[Z]{val: f(v), i: i}
+		}(n.val, i)
+		i++
 	}
 
-	go func() {
-		wg.Wait()
-		close(c)
-	}()
+	mem := make([]Z, i)
+	go waitNClose(&wg, c)
+	for z := range c {
+		mem[z.i] = z.val
+	}
 
 	var results List[Z]
-	for z := range c {
-		results.Push(z)
+	for i, _ := range mem {
+		results.head = &node[Z]{
+			val: mem[i],
+			next: results.head,
+		}
 	}
 	return results
 }
@@ -218,3 +255,23 @@ func (l List[T]) Filter(f func(T) bool) List[T] {
 
 	return passed
 }
+
+type Pair[T any, Z any] struct {
+	Left T
+	Right Z
+}
+
+// Zip takes two lists and joins them to create a list of pairs. It's the same
+// as the python zip function, and totally stupid and Pair should not be in
+// this package but I'm testing the iterable interfaces and this shows they are
+// good, actually
+func Zip[T any, Z any](left List[T], right List[Z]) List[Pair[T, Z]] {
+	lit, rit := left.Iter(), right.Iter()
+	var out List[Pair[T, Z]]
+
+	var next Pair[T, Z]
+	for lit.Next(&next.Left) && rit.Next(&next.Right) {
+		out.head = &node[Pair[T, Z]]{val: next, next: out.head}
+	}
+	return out
+}
diff --git a/list/list_test.go b/list/list_test.go
index 09ad424..4c53630 100644
--- a/list/list_test.go
+++ b/list/list_test.go
@@ -2,6 +2,7 @@ package list
 
 import (
 	"testing"
+	"time"
 )
 
 func TestEmpty(t *testing.T) {
@@ -124,7 +125,18 @@ func TestMap(t *testing.T) {
 	eq(t, 0, nums.At(3))
 
 	eq(t, 30, Max(nums))
+}
+
+func TestRun(t *testing.T) {
+	sleep := func(n int) time.Duration {
+		dur := time.Duration(n) * time.Millisecond
+		time.Sleep(dur)
+		return dur
+	}
 
+	l := Make(1, 2, 3, 4, 5, 4, 3, 2, 1)
+	durs := Run(l, sleep)
+	t.Logf("%v", durs)
 }
 
 func TestIter(t *testing.T) {
diff --git a/span/span.go b/span/span.go
index 259eb39..2b9bff7 100644
--- a/span/span.go
+++ b/span/span.go
@@ -6,6 +6,7 @@ import (
 	"github.com/jordanorelli/generic/iter"
 )
 
+// Span represents some range of integers
 type Span[T constraints.Integer] struct {
 	Start T
 	End T
diff --git a/span/span_test.go b/span/span_test.go
index 95b3466..dabbb99 100644
--- a/span/span_test.go
+++ b/span/span_test.go
@@ -24,7 +24,7 @@ func TestSpan(t *testing.T) {
 	// can be inferred, but when New returns a value of Span[T] (which
 	// satisfies iter.Able[T]), the type parameter cannot be inferred. I don't
 	// know why this behavior exists or if this is the intended behavior.
-	//                +
+	//                |
 	//                |
 	//                V
 	beer := iter.Max[int](New(1, 100))
@@ -37,6 +37,20 @@ func TestSpan(t *testing.T) {
 		t.Errorf("expected 30 to be old but saw %d instead", old)
 	}
 
+	// honestly a very ridiculous use-case, but I'm looking at some weird
+	// inferrence corner cases. It seems the third parameter can't be the
+	// literal 2, you have to explicitly type it.
+	alpha := Step('a', 'z'+1, rune(2))
+
+	// the rune type can't be inferred here either
+	for a, it := iter.Start[rune](alpha); it.Next(&a); {
+		t.Logf("%c", a)
+	}
+
+	// the rune type can't be inferred here either!
+	for a, it := iter.Start[rune](alpha.Iter()); it.Next(&a); {
+	}
+
 	t.Logf("%T", iter.Max[int8](New[int8](3, 10)))
 }