diff --git a/src/main.rs b/src/main.rs
index 845ff9f..fdf5865 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,5 +1,11 @@
+use std::f64::consts;
 use std::{io, io::Write};
 
+const PLANCK_CONSTANT: f64 = 6.62607015e-34f64;
+const ATOMIC_MASS_CONSTANT: f64 = 1.66053906660e-27f64;
+const WIEN_WAVELENGTH_DISPLACEMENT_LAW_CONSTANT: f64 = 2.897771955e-3f64;
+const SPEED_OF_LIGHT_IN_VACUUM: f64 = 299792458f64;
+
 #[derive(Debug, PartialEq)]
 enum TokenizeError {
     NumberParseError(String),
@@ -60,6 +66,11 @@ fn main() {
                 .read_line(&mut input)
                 .expect("Failed to read line");
 
+            if input == "clear\n" {
+                print!("\u{001b}c");
+                continue;
+            }
+
             let result = compute(&input);
             print_result(result);
         }
@@ -88,19 +99,13 @@ impl Token {
 
 fn print_result(result: f64) {
     if result > 10_000. || (result < 0.0001 && result > -0.0001) && result != 0. {
-        println!("{:e}", result);
+        println!("{:E}", result);
     } else {
         println!("{result}");
     }
 }
 
 fn compute(input: &str) -> f64 {
-    let input = &input
-        .trim()
-        .replace(' ', "")
-        .replace("pi", "π")
-        .replace("tau", "τ");
-
     let tokens = match tokenize(input) {
         Ok(v) => v,
         Err(e) => {
@@ -173,7 +178,7 @@ fn tokenize(input: &str) -> Result<Vec<Token>, TokenizeError> {
             '/' | '÷' => Token::Divide,
             '+' => Token::Add,
             '-' | '−' => {
-                // exception for negative exponent for scientific notation
+                // exception for negative exponent in scientific notation
                 if let Some(p) = prev {
                     if p == 'E' {
                         num_buf.push(c);
@@ -185,15 +190,15 @@ fn tokenize(input: &str) -> Result<Vec<Token>, TokenizeError> {
             '^' => Token::Power,
             '%' => Token::Modulus,
             ',' => Token::Separator,
-            'π' => Token::Number(std::f64::consts::PI),
-            'e' => Token::Number(std::f64::consts::E),
-            'τ' => Token::Number(std::f64::consts::TAU),
+            'π' => Token::Number(consts::PI),
+            'τ' => Token::Number(consts::TAU),
             '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9' | 'E' | '.' => {
                 push_buf(&mut tokens, &mut fun_buf)?;
                 num_buf.push(c);
                 prev = Some(c);
                 continue;
             }
+            ' ' | '\n' | '\t' | '\r' => continue,
             _ => {
                 push_buf(&mut tokens, &mut num_buf)?;
                 fun_buf.push(c);
@@ -221,6 +226,7 @@ fn push_buf(tokens: &mut Vec<Token>, buf: &mut String) -> Result<(), TokenizeErr
 }
 
 fn parse_buffer(buf: &str) -> Result<Token, TokenizeError> {
+    // This does not handle implicit multiplication with constants and functions.
     match buf {
         "sin" => Ok(Token::Function(FunctionType::Sine)),
         "cos" => Ok(Token::Function(FunctionType::Cosine)),
@@ -229,6 +235,13 @@ fn parse_buffer(buf: &str) -> Result<Token, TokenizeError> {
         "max" => Ok(Token::Function(FunctionType::Max)),
         "min" => Ok(Token::Function(FunctionType::Min)),
         "sqrt" => Ok(Token::Function(FunctionType::SquareRoot)),
+        "e" => Ok(Token::Number(consts::E)),
+        "pi" => Ok(Token::Number(consts::PI)),
+        "tau" => Ok(Token::Number(consts::TAU)),
+        "h" => Ok(Token::Number(PLANCK_CONSTANT)),
+        "a" => Ok(Token::Number(WIEN_WAVELENGTH_DISPLACEMENT_LAW_CONSTANT)),
+        "u" => Ok(Token::Number(ATOMIC_MASS_CONSTANT)),
+        "c" => Ok(Token::Number(SPEED_OF_LIGHT_IN_VACUUM)),
         _ => {
             if let Ok(number) = buf.parse() {
                 Ok(Token::Number(number))
@@ -285,12 +298,15 @@ fn implicit_operations(tokens: Vec<Token>) -> Option<Vec<Token>> {
             new_tokens.pop();
             new_tokens.pop();
             new_tokens.push(Token::Number(-n));
-        } else if new_tokens[1] == Token::LeftParenthesis {
-            new_tokens.pop();
-            new_tokens.pop();
+        } else if new_tokens[1] == Token::LeftParenthesis
+            || matches!(new_tokens[1], Token::Function(_))
+        {
+            let a = new_tokens[1].clone();
+            new_tokens.pop()?;
+            new_tokens.pop()?;
             new_tokens.push(Token::Number(-1.));
             new_tokens.push(Token::Multiply);
-            new_tokens.push(Token::LeftParenthesis);
+            new_tokens.push(a);
         }
     }
 
@@ -477,8 +493,9 @@ fn calculate(tokens: Vec<Token>) -> Result<f64, CalculateError> {
 #[cfg(test)]
 mod tests {
     use super::*;
+
     #[test]
-    fn token_test() {
+    fn tokens() {
         assert_eq!(tokenize("("), Ok(vec![Token::LeftParenthesis]));
         assert_eq!(tokenize(")"), Ok(vec![Token::RightParenthesis]));
         assert_eq!(tokenize("*"), Ok(vec![Token::Multiply]));
@@ -489,6 +506,14 @@ mod tests {
         assert_eq!(tokenize("3"), Ok(vec![Token::Number(3.)]));
         assert_eq!(tokenize("e"), Ok(vec![Token::Number(std::f64::consts::E)]));
         assert_eq!(tokenize("π"), Ok(vec![Token::Number(std::f64::consts::PI)]));
+        assert_eq!(
+            tokenize("pi"),
+            Ok(vec![Token::Number(std::f64::consts::PI)])
+        );
+        assert_eq!(
+            tokenize("tau"),
+            Ok(vec![Token::Number(std::f64::consts::TAU)])
+        );
         assert_eq!(
             tokenize("max"),
             Ok(vec![Token::Function(FunctionType::Max)])
@@ -507,7 +532,7 @@ mod tests {
         );
         assert_eq!(
             tokenize("ln"),
-            Ok(vec![Token::Function(FunctionType::Log10)])
+            Ok(vec![Token::Function(FunctionType::NaturalLog)])
         );
         assert_eq!(
             tokenize("log"),
@@ -554,8 +579,9 @@ mod tests {
             ])
         );
     }
+
     #[test]
-    fn implicit_test() {
+    fn implicit() {
         // (3)2 == (3)*2
         assert_eq!(
             implicit_operations(vec![
@@ -686,6 +712,7 @@ mod tests {
             ])
         );
     }
+
     #[test]
     fn infix_to_postfix_test() {
         assert_eq!(