diff --git a/src/std/float.no b/src/std/float.no
index 2eab3e3..ddbfd39 100644
--- a/src/std/float.no
+++ b/src/std/float.no
@@ -1,31 +1,33 @@
 pub type Float
 
-pub let neg = fn(float): Float {
-    negFloat(float)
-}
+impl Num for Float {
+    neg = fn(self): Self {
+        negFloat(self)
+    }
 
-pub let abs = fn(float): Float {
-    absFloat(float)
-}
+    abs = fn(self): Self {
+        absFloat(self)
+    }
 
-pub let add = fn(float, other: Float): Float {
-    addFloat(float, other)
-}
+    add = fn(self, other: Self): Self {
+        addFloat(self, other)
+    }
 
-pub let sub = fn(float, other: Float): Float {
-    subFloat(float, other)
-}
+    sub = fn(self, other: Self): Self {
+        subFloat(self, other)
+    }
 
-pub let mult = fn(float, other: Float): Float {
-    multFloat(float, other)
-}
+    mult = fn(self, other: Self): Self {
+        multFloat(self, other)
+    }
 
-pub let div = fn(float, other: Float): Float {
-    divFloat(float, other)
-}
+    div = fn(self, other: Self): Self {
+        divFloat(self, other)
+    }
 
-pub let exp = fn(float, other: Float): Float {
-    expFloat(float, other)
+    exp = fn(self, other: Self): Self {
+        expFloat(self, other)
+    }
 }
 
 impl Eq for Float {
diff --git a/src/std/future/mod.no b/src/std/future/mod.no
index f42be7c..1e52156 100644
--- a/src/std/future/mod.no
+++ b/src/std/future/mod.no
@@ -1,4 +1,6 @@
 use std::ref::eqRef
+use std::list::{ add }
+use std::future::runtime::{ Runtime, runtime }
 
 pub type Future<T>(
     f: fn(resolve: fn(result: T): Unit): Unit, 
@@ -16,8 +18,8 @@ pub type FutureState<T> {
 
 impl <T> Trace for FutureState<T> {}
 
-pub let new = fn<T>(f: fn(resolve: fn(result: T): Unit): Unit): Self {
-    Future(f, [], FutureState::Created())
+pub let new = fn<T>(f: fn(resolve: fn(result: T): Unit): Unit): Future<T> {
+    Future(f, [], Created())
 }
 
 pub let onResolve = fn<T>(future: Future<T>, f: fn(result: T): Unit): Unit {
@@ -37,18 +39,18 @@ pub let onResolve = fn<T>(future: Future<T>, f: fn(result: T): Unit): Unit {
 // TODO: belongs to std::control::Functor
 pub let map = fn<T, U>(future: Future<T>, f: fn(value: T): U): Future<U> {
     // TODO: use .await
-    Future::new(fn(resolve) { future.onResolve(fn(res) { resolve(f(res)) }) })
+    new(fn(resolve) { future.onResolve(fn(res) { resolve(f(res)) }) })
 }
 
 // TODO: belongs to std::control::Monad
 pub let flatMap = fn<T, U>(future: Future<T>, f: fn(value: T): Future<U>): Future<U> {
     // TODO: use .await
-    Future::new(fn(resolve) {
+    new(fn(resolve) {
         future.onResolve(fn (res) { f(res).onResolve(fn(inner) { resolve(inner) }) })
     })
 }
 
-pub let spawn = fn<T>(future: Future<T>, runtime: Runtime): Self {
+pub let spawn = fn<T>(future: Future<T>, runtime: Runtime): Future<T> {
     runtime.spawn(future)
 }
 
diff --git a/src/std/future/runtime.no b/src/std/future/runtime.no
index 8b1fa43..41e6d87 100644
--- a/src/std/future/runtime.no
+++ b/src/std/future/runtime.no
@@ -1,3 +1,8 @@
+use std::future::{ self, FutureState, state, subscribers }
+use std::list::{ add, count, popAt, clear, popFront }
+use std::iter::{ Iter::position }
+use std::ref::eqRef
+
 pub type Runtime(
     // TODO: use std::time::Duration
     pollingRate: Int,
@@ -5,23 +10,23 @@ pub type Runtime(
     pending: List<Future<_>>,
 )
 
-pub let runtime: Runtime = Runtime::new()
+pub let runtime: Runtime = new()
 
 pub let new = fn(): Runtime {
-    Runtime::withPollingRate(10)
+    withPollingRate(10)
 }
 
 pub let withPollingRate = fn(pollingRate: Int): Runtime {
-    Runtime::Runtime(pollingRate, [], [])
+    Runtime(pollingRate, [], [])
 }
 
 pub let loop = fn(runtime): Unit {
     while runtime.queue.count() > 0 {
         let next = runtime.queue.popFront()!
-        next.state = FutureState::Pending()
+        next.state = future::Pending()
         runtime.pending.add(next)
-        let _ = {next.f}(fn(res) {
-            next.state = FutureState::Resolved(res)
+        let _ = {next.future::f}(fn(res) {
+            next.state = future::Resolved(res)
             for s in next.subscribers {
                 s(res)
             }
@@ -39,13 +44,13 @@ pub let loop = fn(runtime): Unit {
 
 pub let spawn = fn<T>(runtime, future: Future<T>): Future<T> {
     runtime.queue.add(future)
-    future.state = FutureState::Queued()
+    future.state = future::Queued()
     future
 }
 
 // TODO: use std::time::Duration
 pub let delay = fn(delay: Int): Future<Unit> {
-    Future::new(fn(resolve) { deferFor(fn() { resolve(unit) }, delay) })
+    future::new(fn(resolve) { deferFor(fn() { resolve(unit) }, delay) })
 }
 
 pub let defer = fn(f: fn(): Unit): Unit {
diff --git a/src/std/int.no b/src/std/int.no
index f4dd761..8121db2 100644
--- a/src/std/int.no
+++ b/src/std/int.no
@@ -1,31 +1,33 @@
 pub type Int
 
-pub let neg = fn(int): Int {
-    negInt(int)
-}
+impl Num for Int {
+    neg = fn(self): Self {
+        negInt(self)
+    }
 
-pub let abs = fn(int): Int {
-    absInt(int)
-}
+    abs = fn(self): Self {
+        absInt(self)
+    }
 
-pub let add = fn(int, other: Int): Int {
-    addInt(int, other)
-}
+    add = fn(self, other: Self): Self {
+        addInt(self, other)
+    }
 
-pub let sub = fn(int, other: Int): Int {
-    subInt(int, other)
-}
+    sub = fn(self, other: Self): Self {
+        subInt(self, other)
+    }
 
-pub let mult = fn(int, other: Int): Int {
-    multInt(int, other)
-}
+    mult = fn(self, other: Self): Self {
+        multInt(self, other)
+    }
 
-pub let div = fn(int, other: Int): Int {
-    divInt(int, other)
-}
+    div = fn(self, other: Self): Self {
+        divInt(self, other)
+    }
 
-pub let exp = fn(int, other: Int): Int {
-    expInt(int, other)
+    exp = fn(self, other: Self): Self {
+        expInt(self, other)
+    }
 }
 
 pub let mod = fn(int, divisor: Int): Int {
diff --git a/src/std/iter/peekable.no b/src/std/iter/peekable.no
index 455a2dd..e0671da 100644
--- a/src/std/iter/peekable.no
+++ b/src/std/iter/peekable.no
@@ -1,3 +1,5 @@
+use std::iter::Iter::next
+
 pub type PeekableIter<T>(
     iter: Iter<T>,
     peeked: Option<Option<T>>
diff --git a/src/std/iter/repeat.no b/src/std/iter/repeat.no
index 3dcc0fc..87b5853 100644
--- a/src/std/iter/repeat.no
+++ b/src/std/iter/repeat.no
@@ -16,6 +16,6 @@ impl <T> Iter<T> for RepeatIter<T> {
 }
 
 pub let repeat = fn<T>(item: T, count: Int): RepeatIter<T> {
-    RepeatIter(range: RangeIter::RangeIter(0, count), item)
+    RepeatIter(range: RangeIter(0, count), item)
 }
 
diff --git a/src/std/num.no b/src/std/num.no
new file mode 100644
index 0000000..b87582a
--- /dev/null
+++ b/src/std/num.no
@@ -0,0 +1,15 @@
+pub trait Num {
+    neg = fn(self): Self
+
+    abs = fn(self): Self
+
+    add = fn(self, other: Self): Self
+
+    sub = fn(self, other: Self): Self
+
+    mult = fn(self, other: Self): Self
+
+    div = fn(self, other: Self): Self
+
+    exp = fn(self, other: Self): Self
+}
diff --git a/src/std/prelude.no b/src/std/prelude.no
index dd5f992..dedbbdc 100644
--- a/src/std/prelude.no
+++ b/src/std/prelude.no
@@ -5,11 +5,12 @@ pub use std::{
     int::{ self, Int },
     string::{ self, String },
     char::{ self, Char },
-    bool::{ self, Bool },
+    bool::{ self, Bool, not },
+    num::Num,
     eq::Eq,
     copy::{ Copy, copy },
     ord::{ Ordering, Ord },
-    iter::{ Iterable, Iter, Collector },
+    iter::{ Iterable::{ self, iter }, Iter, Collector },
     iter::range::range,
     iter::repeat::repeat,
     list::{ self, List },
diff --git a/src/std/string.no b/src/std/string.no
index 9535fb9..61f1a76 100644
--- a/src/std/string.no
+++ b/src/std/string.no
@@ -3,7 +3,7 @@ use std::iter::MapAdapter
 pub type String
 
 // TODO: belongs to the Monoid trait
-pub concat = fn(string: String, other: Self): String {
+pub let concat = fn(string: String, other: String): String {
     concatString(string, other)
 }