diff --git a/src/cli-repl.rs b/src/cli-repl.rs
index 82ace64..4a01e34 100644
--- a/src/cli-repl.rs
+++ b/src/cli-repl.rs
@@ -1,3 +1,4 @@
+use std::f64;
 use std::io::{self, StdoutLock, Write, stdout};
 use std::rc::Rc;
 
@@ -5,7 +6,7 @@ use libopenbirch::environment::Environment;
 use libopenbirch::node::constant::Constant;
 use libopenbirch::node::empty::Empty;
 use libopenbirch::node::{Node, NodeEnum};
-use libopenbirch::parser::{Lexer, Parser, ParserError};
+use libopenbirch::parser::{Lexer, LexerError, Parser, ParserError};
 use malachite::base::num::basic::traits::Zero;
 use malachite::rational::Rational;
 #[cfg(feature = "async")]
@@ -167,6 +168,10 @@ fn main() -> Result<(), io::Error> {
     let mut env = Environment::new();
 
     env.define_native_function("print", print);
+    env.define(
+        "pi",
+        Rc::new(Constant::new(f64::consts::PI.try_into().unwrap()).into()),
+    );
 
     while let Some(source) = input.get()? {
         input.disable_raw()?;
@@ -176,7 +181,9 @@ fn main() -> Result<(), io::Error> {
 
         if tokens_result.is_err() {
             match tokens_result.err().unwrap() {
-                libopenbirch::parser::LexerError::UnexpectedChar(i, exp) => print_err(i, 1, exp),
+                LexerError::UnexpectedChar(i, exp) | LexerError::NumberParse(i, exp) => {
+                    print_err(i, 1, exp)
+                }
             }
             continue;
         }
diff --git a/src/lib/environment.rs b/src/lib/environment.rs
index 3785ce1..074e1e3 100644
--- a/src/lib/environment.rs
+++ b/src/lib/environment.rs
@@ -92,7 +92,8 @@ impl Environment {
         self.stack_depth = 0;
     }
 
-    pub fn define(&mut self, name: String, value: Rc<NodeEnum>) {
+    pub fn define(&mut self, name: impl Into<String>, value: Rc<NodeEnum>) {
+        let name = name.into();
         let id = if let Some(value) = self.str_to_id(&name) {
             *value
         } else {
@@ -110,6 +111,7 @@ impl Environment {
     }
 
     pub fn get(&self, key: &EnvironmentInternalSymbolKey) -> Option<&Rc<NodeEnum>> {
+        eprintln!("Get {key}");
         self.map.get(key)
     }
 
@@ -123,12 +125,11 @@ impl Environment {
     pub fn insert(&mut self, key: EnvironmentInternalSymbolKey, value: Rc<NodeEnum>) {
         if self.stack_depth != 0 {
             let mut shadow = false;
-            if let Some(existing) = self.map.get(&key) {
+            if self.map.get(&key).is_some() {
                 if !self.get_current_scope().contains(&key) {
                     // We need to shadow this variable
                     self.stack_shadows
                         .push((key, self.map.insert(key, value.clone()).unwrap()));
-                    self.stack.push(key);
                     shadow = true;
                 }
             }
diff --git a/src/lib/node/constant.rs b/src/lib/node/constant.rs
index 547c36b..0bbc633 100644
--- a/src/lib/node/constant.rs
+++ b/src/lib/node/constant.rs
@@ -1,5 +1,10 @@
 use std::rc::Rc;
 
+use malachite::{
+    base::{num::basic::traits::Zero, rounding_modes::RoundingMode},
+    rational::{Rational, conversion::primitive_float_from_rational::FloatConversionError},
+};
+
 use super::{Environment, Node, Precedence};
 
 pub type ConstantValue = malachite::rational::Rational;
@@ -21,7 +26,29 @@ impl Node for Constant {
     }
 
     fn as_string(&self, _env: Option<&Environment>) -> String {
-        self.value.to_string()
+        if self.value == Rational::ZERO {
+            return "0".to_owned();
+        }
+
+        if self.value.approx_log() < 50. {
+            let x: Result<f64, FloatConversionError> = self.value.clone().try_into();
+
+            match x {
+                Ok(v) => {
+                    return v.to_string();
+                }
+                Err(_) => {}
+            }
+        }
+
+        if let Some((man, exp, _)) = self
+            .value
+            .sci_mantissa_and_exponent_round_ref::<f64>(RoundingMode::Nearest)
+        {
+            format!("{}*2^{}", man, exp)
+        } else {
+            self.value.to_string()
+        }
     }
 
     fn precedence(&self) -> Precedence {
diff --git a/src/lib/parser/mod.rs b/src/lib/parser/mod.rs
index a5f6c36..b5a7d72 100644
--- a/src/lib/parser/mod.rs
+++ b/src/lib/parser/mod.rs
@@ -101,6 +101,7 @@ pub struct Lexer<'a> {
 #[derive(Debug)]
 pub enum LexerError {
     UnexpectedChar(usize, String),
+    NumberParse(usize, String),
 }
 
 impl<'a> Lexer<'a> {
@@ -137,7 +138,7 @@ impl<'a> Lexer<'a> {
                     loop {
                         let d = self.source.peek();
                         match d {
-                            Some('0'..='9') => {
+                            Some('0'..='9') | Some('e') | Some('E') => {
                                 digit.push(*d.unwrap());
                                 self.source.next();
                                 i += 1;
@@ -160,7 +161,15 @@ impl<'a> Lexer<'a> {
                             }
                         }
                     }
-                    let number = digit.parse::<ConstantValue>().unwrap();
+                    let number =
+                        if let Some(v) = ConstantValue::from_sci_string_simplest(digit.as_str()) {
+                            v
+                        } else {
+                            return Err(LexerError::NumberParse(
+                                i,
+                                format!("Failed to convert {digit} to a number"),
+                            ));
+                        };
 
                     tokens.push(Token(i, TokenType::Number(number)));
                 }
@@ -511,9 +520,7 @@ impl<'a> Parser<'a> {
                         }
                     }
 
-                    return Ok(Function::new(
-                        FunctionType::UserFunction(right, symbols),
-                    ));
+                    return Ok(Function::new(FunctionType::UserFunction(right, symbols)));
                 }
                 _ => {
                     return Err(ParserError::UnexpectedNode(