From 8112d5c2fdfc1352b8068fd5f4a4ed131b5d8379 Mon Sep 17 00:00:00 2001
From: Simon Gardling <titaniumtown@gmail.com>
Date: Wed, 9 Mar 2022 15:50:46 -0500
Subject: [PATCH] warning about E

---
 src/parsing.rs | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/parsing.rs b/src/parsing.rs
index 700e4e1..a0d9383 100644
--- a/src/parsing.rs
+++ b/src/parsing.rs
@@ -120,7 +120,16 @@ pub fn test_func(function_string: &str) -> Option<String> {
                     .collect::<Vec<String>>();
 
                 return match var_names_not_x.len() {
-                    1 => Some(format!("Error: invalid variable: {}", var_names_not_x[0])),
+                    1 => {
+                        let var_name = &var_names_not_x[0];
+                        if var_name == "e" {
+                            Some(String::from(
+                                "If trying to use Euler's number, please use an uppercase E",
+                            ))
+                        } else {
+                            Some(format!("Error: invalid variable: {}", var_name))
+                        }
+                    }
                     _ => Some(format!("Error: invalid variables: {:?}", var_names_not_x)),
                 };
             }