diff --git a/libconlang/examples/fib.rs b/libconlang/examples/fib.rs
new file mode 100644
index 0000000..db45d80
--- /dev/null
+++ b/libconlang/examples/fib.rs
@@ -0,0 +1,16 @@
+// Calculate Fibonacci numbers
+
+fn main() {
+    for num in 0..=30 {
+        println!("fib({num}) = {}", fib(num))
+    }
+}
+
+/// Implements the classic recursive definition of fib()
+fn fib(a: i64) -> i64 {
+    if a > 1 {
+        fib(a - 1) + fib(a - 2)
+    } else {
+        1
+    }
+}
diff --git a/libconlang/src/interpreter.rs b/libconlang/src/interpreter.rs
index 6826229..d115340 100644
--- a/libconlang/src/interpreter.rs
+++ b/libconlang/src/interpreter.rs
@@ -15,7 +15,9 @@ pub trait Callable: std::fmt::Debug {
 }
 
 /// [BuiltIn]s are [Callable]s with bespoke definitions
-pub trait BuiltIn: std::fmt::Debug + Callable {}
+pub trait BuiltIn: std::fmt::Debug + Callable {
+    fn description(&self) -> &str;
+}
 
 pub mod temp_type_impl {
     //! Temporary implementations of Conlang values
@@ -164,6 +166,7 @@ pub mod temp_type_impl {
         String => ConValue::String,
         Function => ConValue::Function,
         Vec<ConValue> => ConValue::Tuple,
+        &'static dyn BuiltIn => ConValue::BuiltIn,
     }
     impl From<()> for ConValue {
         fn from(_: ()) -> Self {
@@ -246,27 +249,6 @@ pub mod temp_type_impl {
             _ => Err(Error::TypeError)?
         ]
     }
-    impl Neg for ConValue {
-        type Output = IResult<Self>;
-        fn neg(self) -> Self::Output {
-            Ok(match self {
-                ConValue::Empty => ConValue::Empty,
-                ConValue::Int(v) => ConValue::Int(-v),
-                _ => Err(Error::TypeError)?,
-            })
-        }
-    }
-    impl Not for ConValue {
-        type Output = IResult<Self>;
-        fn not(self) -> Self::Output {
-            Ok(match self {
-                ConValue::Empty => ConValue::Empty,
-                ConValue::Int(v) => ConValue::Int(!v),
-                ConValue::Bool(v) => ConValue::Bool(!v),
-                _ => Err(Error::TypeError)?,
-            })
-        }
-    }
     impl std::fmt::Display for ConValue {
         fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
             match self {
@@ -301,7 +283,7 @@ pub mod temp_type_impl {
                     write!(f, "fn {}", func.name())
                 }
                 ConValue::BuiltIn(func) => {
-                    write!(f, "internal fn {}", func.name())
+                    write!(f, "{}", func.description())
                 }
             }
         }
@@ -499,48 +481,51 @@ pub mod interpret {
         fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
             let Binary { head, tail } = self;
             let mut head = head.interpret(env)?;
+            // Short-circuiting ops
             for (op, tail) in tail {
-                head = match op {
+                match op {
                     BinaryKind::LogAnd => {
                         if head.truthy()? {
-                            tail.interpret(env)
-                        } else {
-                            return Ok(head); // Short circuiting
+                            head = tail.interpret(env)?;
+                            continue;
                         }
+                        return Ok(head); // Short circuiting
                     }
                     BinaryKind::LogOr => {
                         if !head.truthy()? {
-                            tail.interpret(env)
-                        } else {
-                            return Ok(head); // Short circuiting
+                            head = tail.interpret(env)?;
+                            continue;
                         }
+                        return Ok(head); // Short circuiting
                     }
                     BinaryKind::LogXor => {
-                        // TODO: It should be possible to assemble better error information from
-                        // this
-                        let (lhs, rhs) = (head.truthy()?, tail.interpret(env)?.truthy()?);
-                        Ok(ConValue::Bool(lhs ^ rhs))
+                        head = ConValue::Bool(head.truthy()? ^ tail.interpret(env)?.truthy()?);
+                        continue;
                     }
-                    // TODO: For all overloadable operators, transmute into function call
-                    BinaryKind::Mul => head * tail.interpret(env)?,
-                    BinaryKind::Div => head / tail.interpret(env)?,
-                    BinaryKind::Rem => head % tail.interpret(env)?,
-                    BinaryKind::Add => head + tail.interpret(env)?,
-                    BinaryKind::Sub => head - tail.interpret(env)?,
-                    BinaryKind::Shl => head << tail.interpret(env)?,
-                    BinaryKind::Shr => head >> tail.interpret(env)?,
-                    BinaryKind::BitAnd => head & tail.interpret(env)?,
-                    BinaryKind::BitOr => head | tail.interpret(env)?,
-                    BinaryKind::BitXor => head ^ tail.interpret(env)?,
-                    BinaryKind::RangeExc => head.range_exc(tail.interpret(env)?),
-                    BinaryKind::RangeInc => head.range_inc(tail.interpret(env)?),
-                    BinaryKind::Lt => head.lt(&tail.interpret(env)?),
-                    BinaryKind::LtEq => head.lt_eq(&tail.interpret(env)?),
-                    BinaryKind::Equal => head.eq(&tail.interpret(env)?),
-                    BinaryKind::NotEq => head.neq(&tail.interpret(env)?),
-                    BinaryKind::GtEq => head.gt_eq(&tail.interpret(env)?),
-                    BinaryKind::Gt => head.gt(&tail.interpret(env)?),
+                    _ => {}
+                }
+                let tail = tail.interpret(env)?;
+                head = match op {
+                    BinaryKind::Mul => env.call("mul", &[head, tail]),
+                    BinaryKind::Div => env.call("div", &[head, tail]),
+                    BinaryKind::Rem => env.call("rem", &[head, tail]),
+                    BinaryKind::Add => env.call("add", &[head, tail]),
+                    BinaryKind::Sub => env.call("sub", &[head, tail]),
+                    BinaryKind::Shl => env.call("shl", &[head, tail]),
+                    BinaryKind::Shr => env.call("shr", &[head, tail]),
+                    BinaryKind::BitAnd => env.call("and", &[head, tail]),
+                    BinaryKind::BitOr => env.call("or", &[head, tail]),
+                    BinaryKind::BitXor => env.call("xor", &[head, tail]),
+                    BinaryKind::RangeExc => env.call("range_exc", &[head, tail]),
+                    BinaryKind::RangeInc => env.call("range_inc", &[head, tail]),
+                    BinaryKind::Lt => env.call("lt", &[head, tail]),
+                    BinaryKind::LtEq => env.call("lt_eq", &[head, tail]),
+                    BinaryKind::Equal => env.call("eq", &[head, tail]),
+                    BinaryKind::NotEq => env.call("noteq", &[head, tail]),
+                    BinaryKind::GtEq => env.call("gt_eq", &[head, tail]),
+                    BinaryKind::Gt => env.call("gt", &[head, tail]),
                     BinaryKind::Dot => todo!("search within a type's namespace!"),
+                    _ => Ok(head),
                 }?;
             }
             Ok(head)
@@ -553,9 +538,9 @@ pub mod interpret {
 
             for op in ops.iter().rev() {
                 operand = match op {
-                    UnaryKind::Deref => todo!("Deref operator"),
-                    UnaryKind::Neg => (-operand)?,
-                    UnaryKind::Not => (!operand)?,
+                    UnaryKind::Deref => env.call("deref", &[operand])?,
+                    UnaryKind::Neg => env.call("neg", &[operand])?,
+                    UnaryKind::Not => env.call("not", &[operand])?,
                     UnaryKind::At => {
                         println!("{operand}");
                         operand
@@ -646,7 +631,8 @@ pub mod interpret {
     }
     impl Interpret for AddrOf {
         fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
-            todo!("Implement AddrOf in {env}")
+            let Self { count: _, mutable: _, expr } = self;
+            todo!("Create reference\nfrom expr: {expr}\nin env:\n{env}\n")
         }
     }
     impl Interpret for Block {
@@ -809,77 +795,16 @@ pub mod function {
     }
 }
 
-pub mod builtin {
-    //! Implementations of built-in functions
-    mod builtin_imports {
-        pub use crate::interpreter::{
-            env::Environment, error::IResult, temp_type_impl::ConValue, BuiltIn, Callable,
-        };
-    }
-    use super::BuiltIn;
-    /// Builtins to load when a new interpreter is created
-    pub const DEFAULT_BUILTINS: &[&dyn BuiltIn] = &[&print::Print, &dbg::Dbg, &dump::Dump];
-
-    mod print {
-        //! Implements the unstable `print(...)` builtin
-        use super::builtin_imports::*;
-        /// Implements the `print(...)` builtin
-        #[derive(Clone, Debug)]
-        pub struct Print;
-        impl BuiltIn for Print {}
-        #[rustfmt::skip]
-        impl Callable for Print {
-            fn name(&self) -> &'static str { "print" }
-            fn call(&self, _inter: &mut Environment, args: &[ConValue]) -> IResult<ConValue> {
-                for arg in args {
-                    print!("{arg}")
-                }
-                println!();
-                Ok(ConValue::Empty)
-            }
-        }
-    }
-    mod dbg {
-        //! Implements the unstable `dbg(...)` builtin
-        use super::builtin_imports::*;
-        #[derive(Clone, Debug)]
-        pub struct Dbg;
-        impl BuiltIn for Dbg {}
-        #[rustfmt::skip]
-        impl Callable for Dbg {
-            fn name(&self) -> &str { "dbg" }
-            fn call(&self, _inter: &mut Environment, args: &[ConValue]) -> IResult<ConValue> {
-                println!("{args:?}");
-                Ok(args.into())
-            }
-        }
-    }
-    mod dump {
-        use super::builtin_imports::*;
-        #[derive(Clone, Debug)]
-        pub struct Dump;
-        impl BuiltIn for Dump {}
-        impl Callable for Dump {
-            fn call(&self, env: &mut Environment, _args: &[ConValue]) -> IResult<ConValue> {
-                println!("{}", *env);
-                Ok(ConValue::Empty)
-            }
-
-            fn name(&self) -> &str {
-                "dump"
-            }
-        }
-    }
-}
+pub mod builtin;
 
 pub mod env {
     //! Lexical and non-lexical scoping for variables
     use super::{
-        builtin::DEFAULT_BUILTINS,
+        builtin::{BINARY, MISC, RANGE, UNARY},
         error::{Error, IResult},
         function::Function,
         temp_type_impl::ConValue,
-        Callable, Interpret,
+        BuiltIn, Callable, Interpret,
     };
     use crate::ast::{Function as FnDecl, Identifier};
     use std::{
@@ -899,9 +824,9 @@ pub mod env {
             for (frame, name) in self.frames.iter().rev() {
                 writeln!(f, "--- {name} ---")?;
                 for (var, val) in frame {
-                    write!(f, "- {var}: ")?;
+                    write!(f, "{var}: ")?;
                     match val {
-                        Some(value) => writeln!(f, "{value}"),
+                        Some(value) => writeln!(f, "\t{value}"),
                         None => writeln!(f, "<undefined>"),
                     }?
                 }
@@ -911,14 +836,22 @@ pub mod env {
     }
     impl Default for Environment {
         fn default() -> Self {
-            let mut builtins = HashMap::new();
-            for &builtin in DEFAULT_BUILTINS {
-                builtins.insert(builtin.name().into(), Some(ConValue::BuiltIn(builtin)));
+            Self {
+                frames: vec![
+                    (to_hashmap(RANGE), "range ops"),
+                    (to_hashmap(UNARY), "unary ops"),
+                    (to_hashmap(BINARY), "binary ops"),
+                    (to_hashmap(MISC), "builtins"),
+                    (HashMap::new(), "globals"),
+                ],
             }
-            // FIXME: Temporary until modules are implemented
-            Self { frames: vec![(builtins, "builtins"), (HashMap::new(), "globals")] }
         }
     }
+    fn to_hashmap(from: &[&'static dyn BuiltIn]) -> HashMap<String, Option<ConValue>> {
+        from.iter()
+            .map(|&v| (v.name().into(), Some(v.into())))
+            .collect()
+    }
 
     impl Environment {
         pub fn new() -> Self {
@@ -1073,7 +1006,11 @@ pub mod error {
         /// A value was called, but is not callable
         NotCallable(ConValue),
         /// A function was called with the wrong number of arguments
-        ArgNumber { want: usize, got: usize },
+        ArgNumber {
+            want: usize,
+            got: usize,
+        },
+        NullPointer,
     }
 
     impl std::error::Error for Error {}
@@ -1109,6 +1046,9 @@ pub mod error {
                 Error::ArgNumber { want, got } => {
                     write!(f, "Expected {want} arguments, got {got}")
                 }
+                Error::NullPointer => {
+                    write!(f, "Attempted to dereference a null pointer?")
+                }
             }
         }
     }
diff --git a/libconlang/src/interpreter/builtin.rs b/libconlang/src/interpreter/builtin.rs
new file mode 100644
index 0000000..ede42bc
--- /dev/null
+++ b/libconlang/src/interpreter/builtin.rs
@@ -0,0 +1,239 @@
+//! Implementations of built-in functions
+
+use super::{
+    env::Environment,
+    error::{Error, IResult},
+    temp_type_impl::ConValue,
+    BuiltIn, Callable,
+};
+use std::io::{stdout, Write};
+
+builtins! {
+    const MISC;
+    /// Unstable variadic print function
+    pub fn print<_, args> () -> IResult<ConValue> {
+        let mut out = stdout().lock();
+        for arg in args {
+            write!(out, "{arg}").ok();
+        }
+        writeln!(out).ok();
+        Ok(ConValue::Empty)
+    }
+    /// Prints the [Debug](std::fmt::Debug) version of the input values
+    pub fn dbg<_, args> () -> IResult<ConValue> {
+        let mut out = stdout().lock();
+        for arg in args {
+            writeln!(out, "{arg:?}").ok();
+        }
+        Ok(args.into())
+    }
+    /// Dumps info from the environment
+    pub fn dump<env, _>() -> IResult<ConValue> {
+        println!("{}", *env);
+        Ok(ConValue::Empty)
+    }
+}
+builtins! {
+    const BINARY;
+    /// Multiplication `a * b`
+    pub fn mul(lhs, rhs) -> IResult<ConValue> {
+        Ok(match (lhs, rhs) {
+            (ConValue::Empty, ConValue::Empty) => ConValue::Empty,
+            (ConValue::Int(a), ConValue::Int(b)) => ConValue::Int(a * b),
+            _ => Err(Error::TypeError)?
+        })
+    }
+    /// Division `a / b`
+    pub fn div(lhs, rhs) -> IResult<ConValue> {
+        Ok(match (lhs, rhs){
+            (ConValue::Empty, ConValue::Empty) => ConValue::Empty,
+            (ConValue::Int(a), ConValue::Int(b)) => ConValue::Int(a / b),
+            _ => Err(Error::TypeError)?
+        })
+    }
+    /// Remainder `a % b`
+    pub fn rem(lhs, rhs) -> IResult<ConValue> {
+        Ok(match (lhs, rhs) {
+            (ConValue::Empty, ConValue::Empty) => ConValue::Empty,
+            (ConValue::Int(a), ConValue::Int(b)) => ConValue::Int(a % b),
+            _ => Err(Error::TypeError)?,
+        })
+    }
+
+    /// Addition `a + b`
+    pub fn add(lhs, rhs) -> IResult<ConValue> {
+        Ok(match (lhs, rhs) {
+            (ConValue::Empty, ConValue::Empty) => ConValue::Empty,
+            (ConValue::Int(a), ConValue::Int(b)) => ConValue::Int(a + b),
+            (ConValue::String(a), ConValue::String(b)) => ConValue::String(a.to_string() + b),
+            _ => Err(Error::TypeError)?
+        })
+    }
+    /// Subtraction `a - b`
+    pub fn sub(lhs, rhs) -> IResult<ConValue> {
+        Ok(match (lhs, rhs) {
+            (ConValue::Empty, ConValue::Empty) => ConValue::Empty,
+            (ConValue::Int(a), ConValue::Int(b)) => ConValue::Int(a - b),
+            _ => Err(Error::TypeError)?,
+        })
+    }
+
+    /// Shift Left `a << b`
+    pub fn shl(lhs, rhs) -> IResult<ConValue> {
+        Ok(match (lhs, rhs) {
+            (ConValue::Empty, ConValue::Empty) => ConValue::Empty,
+            (ConValue::Int(a), ConValue::Int(b)) => ConValue::Int(a << b),
+            _ => Err(Error::TypeError)?,
+        })
+    }
+    /// Shift Right `a >> b`
+    pub fn shr(lhs, rhs) -> IResult<ConValue> {
+        Ok(match (lhs, rhs) {
+            (ConValue::Empty, ConValue::Empty) => ConValue::Empty,
+            (ConValue::Int(a), ConValue::Int(b)) => ConValue::Int(a >> b),
+            _ => Err(Error::TypeError)?,
+        })
+    }
+
+    /// Bitwise And `a & b`
+    pub fn and(lhs, rhs) -> IResult<ConValue> {
+        Ok(match (lhs, rhs) {
+            (ConValue::Empty, ConValue::Empty) => ConValue::Empty,
+            (ConValue::Int(a), ConValue::Int(b)) => ConValue::Int(a & b),
+            (ConValue::Bool(a), ConValue::Bool(b)) => ConValue::Bool(a & b),
+            _ => Err(Error::TypeError)?,
+        })
+    }
+    /// Bitwise Or `a | b`
+    pub fn or(lhs, rhs) -> IResult<ConValue> {
+        Ok(match (lhs, rhs) {
+            (ConValue::Empty, ConValue::Empty) => ConValue::Empty,
+            (ConValue::Int(a), ConValue::Int(b)) => ConValue::Int(a | b),
+            (ConValue::Bool(a), ConValue::Bool(b)) => ConValue::Bool(a | b),
+            _ => Err(Error::TypeError)?,
+        })
+    }
+    /// Bitwise Exclusive Or `a ^ b`
+    pub fn xor(lhs, rhs) -> IResult<ConValue> {
+        Ok(match (lhs, rhs) {
+            (ConValue::Empty, ConValue::Empty) => ConValue::Empty,
+            (ConValue::Int(a), ConValue::Int(b)) => ConValue::Int(a ^ b),
+            (ConValue::Bool(a), ConValue::Bool(b)) => ConValue::Bool(a ^ b),
+            _ => Err(Error::TypeError)?,
+        })
+    }
+
+    /// Tests whether `a < b`
+    pub fn lt(lhs, rhs) -> IResult<ConValue> {
+        cmp!(lhs, rhs, false, <)
+    }
+    /// Tests whether `a <= b`
+    pub fn lt_eq(lhs, rhs) -> IResult<ConValue> {
+        cmp!(lhs, rhs, true, <=)
+    }
+    /// Tests whether `a == b`
+    pub fn eq(lhs, rhs) -> IResult<ConValue> {
+        cmp!(lhs, rhs, true, ==)
+    }
+    /// Tests whether `a != b`
+    pub fn neq(lhs, rhs) -> IResult<ConValue> {
+        cmp!(lhs, rhs, false, !=)
+    }
+    /// Tests whether `a <= b`
+    pub fn gt_eq(lhs, rhs) -> IResult<ConValue> {
+        cmp!(lhs, rhs, true, >=)
+    }
+    /// Tests whether `a < b`
+    pub fn gt(lhs, rhs) -> IResult<ConValue> {
+        cmp!(lhs, rhs, false, >)
+    }
+}
+builtins! {
+    const RANGE;
+    /// Exclusive Range `a..b`
+    pub fn range_exc(lhs, rhs) -> IResult<ConValue> {
+        let (&ConValue::Int(lhs), &ConValue::Int(rhs)) = (lhs, rhs) else {
+            Err(Error::TypeError)?
+        };
+        Ok(ConValue::RangeExc(lhs, rhs.saturating_sub(1)))
+    }
+    /// Inclusive Range `a..=b`
+    pub fn range_inc(lhs, rhs) -> IResult<ConValue> {
+        let (&ConValue::Int(lhs), &ConValue::Int(rhs)) = (lhs, rhs) else {
+            Err(Error::TypeError)?
+        };
+        Ok(ConValue::RangeInc(lhs, rhs))
+    }
+}
+builtins! {
+    const UNARY;
+    /// Negates the ConValue
+    pub fn neg(tail) -> IResult<ConValue> {
+        Ok(match tail {
+            ConValue::Empty => ConValue::Empty,
+            ConValue::Int(v) => ConValue::Int(-v),
+            _ => Err(Error::TypeError)?,
+        })
+    }
+    /// Inverts the ConValue
+    pub fn not(tail) -> IResult<ConValue> {
+        Ok(match tail {
+            ConValue::Empty => ConValue::Empty,
+            ConValue::Int(v) => ConValue::Int(!v),
+            ConValue::Bool(v) => ConValue::Bool(!v),
+            _ => Err(Error::TypeError)?,
+        })
+    }
+}
+
+/// Turns an argument slice into an array with the (inferred) correct number of elements
+pub fn to_args<const N: usize>(args: &[ConValue]) -> IResult<&[ConValue; N]> {
+    args.try_into()
+        .map_err(|_| Error::ArgNumber { want: N, got: args.len() })
+}
+
+/// Turns function definitions into ZSTs which implement [Callable] and [BuiltIn]
+macro builtins (
+    $(prefix = $prefix:literal)?
+    const $defaults:ident $( = [$($additional_builtins:expr),*$(,)?])?;
+    $(
+        $(#[$meta:meta])*$vis:vis fn $name:ident$(<$env:tt, $args:tt>)? ( $($($arg:tt),+$(,)?)? ) $(-> $rety:ty)?
+            $body:block
+    )*
+) {
+    /// Builtins to load when a new interpreter is created
+    pub const $defaults: &[&dyn BuiltIn] = &[$(&$name,)* $($additional_builtins)*];
+    $(
+        $(#[$meta])* #[allow(non_camel_case_types)] #[derive(Clone, Debug)]
+        /// ```rust,ignore
+        #[doc = stringify!(builtin! fn $name($($($arg),*)?) $(-> $rety)? $body)]
+        /// ```
+        $vis struct $name;
+        impl BuiltIn for $name {
+            fn description(&self) -> &str { concat!("builtin ", stringify!($name), stringify!(($($($arg),*)?) )) }
+        }
+        impl Callable for $name {
+            #[allow(unused)]
+            fn call(&self, env: &mut Environment, args: &[ConValue]) $(-> $rety)? {
+                // println!("{}", stringify!($name), );
+                $(let $env = env;
+                let $args = args;)?
+                $(let [$($arg),*] = to_args(args)?;)?
+                $body
+            }
+            fn name(&self) -> &str { stringify!($name) }
+        }
+    )*
+}
+
+/// Templates comparison functions for [ConValue]
+macro cmp ($a:expr, $b:expr, $empty:literal, $op:tt) {
+    match ($a, $b) {
+        (ConValue::Empty, ConValue::Empty) => Ok(ConValue::Bool($empty)),
+        (ConValue::Int(a), ConValue::Int(b)) => Ok(ConValue::Bool(a $op b)),
+        (ConValue::Bool(a), ConValue::Bool(b)) => Ok(ConValue::Bool(a $op b)),
+        (ConValue::Char(a), ConValue::Char(b)) => Ok(ConValue::Bool(a $op b)),
+        (ConValue::String(a), ConValue::String(b)) => Ok(ConValue::Bool(a $op b)),
+        _ => Err(Error::TypeError)
+    }
+}
diff --git a/sample-code/fibonacci.cl b/sample-code/fib.cl
similarity index 60%
rename from sample-code/fibonacci.cl
rename to sample-code/fib.cl
index 75444e1..44a6eb0 100644
--- a/sample-code/fibonacci.cl
+++ b/sample-code/fib.cl
@@ -1,12 +1,13 @@
 // Calculate Fibonacci numbers
 
-fn main() -> i128 {
-    let num = 10;
-    print("fib(", num, "): ", fib(num));
+fn main() {
+    for num in 0..=30 {
+        print("fib(", num, ") = ", fib(num))
+    }
 }
 
 /// Implements the classic recursive definition of fib()
-fn fib(a: i128) -> i128 {
+fn fib(a: i64) -> i64 {
     if a > 1 {
         fib(a - 1) + fib(a - 2)
     } else {