diff --git a/Cargo.toml b/Cargo.toml
index fecd6ea..f246e7b 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -27,7 +27,7 @@ include-flate = { git = "https://github.com/Titaniumtown/include-flate.git" }
 shadow-rs = { version = "0.9", default-features = false }
 const_format = { version = "0.2.22", default-features = false, features = ["fmt"] }
 cfg-if = "1.0.0"
-meval = { git = "https://github.com/Titaniumtown/meval-rs.git" }
+exmex = { git = "https://github.com/bertiqwerty/exmex.git", branch = "main", features = ["partial"] }
 
 [build-dependencies]
 shadow-rs = "0.9"
diff --git a/src/egui_app.rs b/src/egui_app.rs
index ae382c8..d67489b 100644
--- a/src/egui_app.rs
+++ b/src/egui_app.rs
@@ -271,7 +271,7 @@ impl MathApp {
                         | self.last_error.iter().any(|ele| ele.0 == i)
                     {
                         // let proc_func_str = self.func_strs[i].clone();
-                        let func_test_output = test_func(proc_func_str.clone());
+                        let func_test_output = test_func(&proc_func_str);
                         if let Some(test_output_value) = func_test_output {
                             self.last_error.push((i, test_output_value));
                         } else {
diff --git a/src/parsing.rs b/src/parsing.rs
index e31708c..0ac0632 100644
--- a/src/parsing.rs
+++ b/src/parsing.rs
@@ -1,39 +1,28 @@
-use meval::Expr;
-
-pub const EPSILON: f64 = 5.0e-7;
-pub const DOUBLE_EPSILON: f64 = 10.0e-7;
-
-type BoxFunction = Box<dyn Fn(f64) -> f64>;
+use exmex::prelude::*;
 
 pub struct BackingFunction {
-    function: BoxFunction,
+    function: FlatEx<f64>,
+    derivative: FlatEx<f64>,
 }
 
 impl BackingFunction {
     pub fn new(func_str: &str) -> Self {
+        let function = exmex::parse::<f64>(func_str).unwrap();
         Self {
-            function: Box::new({
-                let expr: Expr = func_str.parse().unwrap();
-                expr.bind("x").unwrap()
-            }),
+            function: function.clone(),
+            derivative: function.partial(0).unwrap(),
         }
     }
 
-    pub fn get(&self, x: f64) -> f64 { (self.function)(x) }
+    pub fn get(&self, x: f64) -> f64 { self.function.eval(&[x]).unwrap_or(f64::NAN) }
 
     pub fn derivative(&self, x: f64, n: u64) -> f64 {
         if n == 0 {
-            return self.get(x);
-        }
-
-        let (y1, y2) = (
-            self.derivative(x - EPSILON, n - 1),
-            (self.derivative(x + EPSILON, n - 1)),
-        );
-
-        match y1 == y2 {
-            true => 0.0,
-            false => (y2 - y1) / DOUBLE_EPSILON,
+            self.get(x)
+        } else if n == 1 {
+            self.derivative.eval(&[x]).unwrap_or(f64::NAN)
+        } else {
+            panic!("n > 1");
         }
     }
 }
@@ -110,33 +99,11 @@ pub fn add_asterisks(function_in: String) -> String {
 }
 
 // Tests function to make sure it's able to be parsed. Returns the string of the Error produced, or an empty string if it runs successfully.
-pub fn test_func(function_string: String) -> Option<String> {
-    // Factorials do not work, and it would be really difficult to make them work
-    if function_string.contains('!') {
-        return Some("Factorials are unsupported".to_string());
-    }
-
-    let new_func_str: String = add_asterisks(function_string);
-    let expr_result = new_func_str.parse();
-    let expr_error = match &expr_result {
+pub fn test_func(function_string: &str) -> Option<String> {
+    match exmex::parse::<f64>(function_string) {
+        Err(e) => Some(e.to_string()),
         Ok(_) => None,
-        Err(error) => Some(format!("{}", error)),
-    };
-    if expr_error.is_some() {
-        return expr_error;
     }
-
-    let expr: Expr = expr_result.unwrap();
-    let func_result = expr.bind("x");
-    let func_error = match &func_result {
-        Ok(_) => None,
-        Err(error) => Some(format!("{}", error)),
-    };
-    if func_error.is_some() {
-        return func_error;
-    }
-
-    None
 }
 
 // Tests to make sure my cursed function works as intended