diff --git a/dm_lib/std/collections/collection.dm b/dm_lib/std/collections/collection.dm
index bcdf014..2761ebd 100644
--- a/dm_lib/std/collections/collection.dm
+++ b/dm_lib/std/collections/collection.dm
@@ -1,6 +1,5 @@
 ns std::collections
 
-pub int Collection<T : PartialEq> : Monad {
+pub int Collection<T> : Monad {
     size: Int
-    fn contains(element: T): Bool
 }
diff --git a/dm_lib/std/collections/list.dm b/dm_lib/std/collections/list.dm
index 03a4dcf..83ab2d3 100644
--- a/dm_lib/std/collections/list.dm
+++ b/dm_lib/std/collections/list.dm
@@ -2,82 +2,54 @@ ns std::collections
 
 use std::collections::Collection
 
-pub int List<T : PartialEq> : Collection<T> {
-    fn add(element: T)
-    fn remove(element: T)
-
-    fn index_of(element: T): Option<Int>
+pub int Stack<T> : Collection<T> {
+    fn push(element: T)
+    fn pop(): Option<T>
     fn get_at(index: Int): Option<T>
-    fn remove_at(index: Int): Option<T>
 }
 
-// This implies that Int, Long, and Double don't implement Zero, because 0 could reasonably mean something
-// whereas Unit means "null" for objects
-pub impl ArrayList<T : PartialEq> : List<T> {
+pub impl ArrayStack<T : Default | Empty> : Stack<T> {
+    fld arr: mut Array<T> = array::of_length(16, std::reflect::default_or_empty<T>)
+    fld current_index: mut Int = 0
 
-    mut fld arr: Array<T>
-    mut fld current_index: Int = 0
-    fld zero: Zero<T>
-
-    pub ctor(items: Array<T>, zero: Zero<T>) {
-        arr = items
-        self.zero = zero
+    impl fn <U> map(m) {
+        let result: mut Array<U> = array::of_length(arr.length, std::reflect::default_or_empty<U>)
+        for (element, i) in arr.iter_with_indices() {
+            result[i] = m(element)
+        }
+        result
     }
 
-    pub ctor(size: Int, zero: Zero<T>) {
-        arr = array::with_size(size, zero)
-        self.zero = zero
+    impl fn <U> flat_map(m) {
+        let result: mut Array<U> = array::of_length(arr.length, std::reflect::default_or_empty<Array<U>>)
+        for (element, i) in arr.iter_with_indices() {
+            result[i] = m(element)
+        }
+        array::flatten(result)
     }
 
-    pub ctor(zero: Zero<T>) {
-        arr = array::with_size(8, zero)
-        self.zero = zero
-    }
+    impl fn get_size() = current_index
 
-    impl fn add(element) {
+    impl fn push(element) {
         if current_index == arr.length {
-            arr = array::clone_with_size(arr.length * 2, zero)
+            arr = array::clone(size = arr.length * 2, source = arr)
         }
         arr[current_index] = element
         current_index++
     }
 
-    impl fn remove(element) {
-        let index = index_of(element).get_or_throw(() => NoSuchElementException())
-        arr[index] = T::default
-    }
-
-    impl fn index_of(element) {
-        for (e, index) in arr.iter_with_index() {
-            if e == element {
-                return Some(index)
-            }
+    impl fn pop() {
+        if current_index > 0 {
+            let element = arr[current_index - 1]
+            current_index--
+            return Some(element)
         }
         None
     }
 
-    impl fn get_at(index) {
-        if index >= arr.length || index < 0 {
-            return None
-        }
-        let item = arr[index]
-        item == zero ? None : Some(item)
-    }
-
-    impl fn remove_at(index) {
-        if index <= arr.length || index < 0 {
-            return None
-        }
-        let element = arr[index]
-        if element == zero {
-            return None
-        }
-        arr[index] = zero.item
-        Some(element)
-    }
-
+    impl fn get_at(index) = index < arr.length ? Some(arr[index]) : None
 }
 
-pub mod list {
+pub mod stack {
     pub fn of<T : PartialEq>(items: ...T): List<T> = ArrayList(items)
 }
diff --git a/dm_lib/std/core/array.dm b/dm_lib/std/core/array.dm
index c4ae9b2..60650a5 100644
--- a/dm_lib/std/core/array.dm
+++ b/dm_lib/std/core/array.dm
@@ -1,6 +1,9 @@
 ns std::core
 
-pub int Array<T> : Monad {
+pub int Array<T> : Monad + Default + Empty {
+    const default = array::empty<Self>
+    const empty = array::empty<Self>
+
     length: Int
 }
 
@@ -9,6 +12,24 @@ pub mod array {
     // Usage:
     // let int_array = array::of(1, 2, 3)
     // assert_eq(3, int_array.length)
-    decl pub fn of<T>(ts: ...T): Array<T>
+    pub extern fn of<T>(ts: ...T): Array<T>
+
+    pub extern fn of_length<T>(length: Int, init_value: T): Array<T>
+
+    pub extern fn empty<T>(): Array<T>
+
+    pub fn flatten<T>(ats: Array<Array<T>>): Array<T> {
+        let total_ts = ats.map { ts -> ts.length }
+            .reduce { acc, current -> acc + current }
+        let result: mut Array<T> = of_length(total_ts, std::reflect::default_or_empty<T>)
+        let i: mut Int = 0
+        for a in ats {
+            for element in a {
+                result[i] = element
+                i++
+            }
+        }
+        result
+    }
 
 }
diff --git a/dm_lib/std/core/character.dm b/dm_lib/std/core/character.dm
index 431472f..a08dfd4 100644
--- a/dm_lib/std/core/character.dm
+++ b/dm_lib/std/core/character.dm
@@ -8,6 +8,6 @@ pub int Character : Display {
 }
 
 pub impl Utf8Character(bytes: Array<Byte>) {
-    impl fn get_encoding() = Encoding::Utf8
+    encoding = Encoding::Utf8
     impl fn to_string() = string::from_utf8_bytes(bytes)
 }
diff --git a/dm_lib/std/core/cls.dm b/dm_lib/std/core/cls.dm
new file mode 100644
index 0000000..d3f1615
--- /dev/null
+++ b/dm_lib/std/core/cls.dm
@@ -0,0 +1,14 @@
+ns std::core
+
+pub cls Any {
+    fqn: String
+    simple_name: String
+}
+
+pub cls Default {
+    default: Self
+}
+
+pub cls Empty {
+    empty: Self
+}
diff --git a/dm_lib/std/core/print.dm b/dm_lib/std/core/print.dm
index 0b5c401..ce19518 100644
--- a/dm_lib/std/core/print.dm
+++ b/dm_lib/std/core/print.dm
@@ -1,5 +1,7 @@
 ns std::core
 
-decl pub fn print(message: Any)
+extern fn _print(message: Any)
+extern fn _println(message: Any)
 
-decl pub fn println(message: Any)
+pub fn print(message: Any) = _print(message)
+pub fn println(message: Any) = _println(message)
diff --git a/dm_lib/std/core/string.dm b/dm_lib/std/core/string.dm
index c07d330..317c26f 100644
--- a/dm_lib/std/core/string.dm
+++ b/dm_lib/std/core/string.dm
@@ -14,9 +14,11 @@ pub int String : Display {
 }
 
 impl Utf8String(bytes: Array<Byte>) : String {
-    impl fn get_encoding() = Encoding::Utf8
-    impl fn get_length() = bytes.length
-    impl fn get_characters() = todo('parse the utf8 bytes and return an Array<Character>')
+    encoding = Encoding::Utf8
+    length = bytes.length
+    characters = lazy {
+        todo('parse the utf8 bytes and return an Array<Character>')
+    }
 }
 
 pub mod string {
diff --git a/dm_lib/std/reflect/util.dm b/dm_lib/std/reflect/util.dm
new file mode 100644
index 0000000..3810cd8
--- /dev/null
+++ b/dm_lib/std/reflect/util.dm
@@ -0,0 +1,6 @@
+ns std::reflect
+
+pub fn <T> default_or_empty() {
+    T is Default ? T::default : T is Empty
+        ? T::empty : throw IllegalArgumentException("Type ${T::fqn} extends neither Default nor Empty.")
+}
\ No newline at end of file