From f775f643573152ae9002a6a795e83cbde0a001a4 Mon Sep 17 00:00:00 2001
From: Simon Gardling <titaniumtown@gmail.com>
Date: Tue, 17 May 2022 08:46:58 -0400
Subject: [PATCH] change get_nth_derivative_str

---
 parsing/src/parsing.rs | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/parsing/src/parsing.rs b/parsing/src/parsing.rs
index f16a5f7..d8390d1 100644
--- a/parsing/src/parsing.rs
+++ b/parsing/src/parsing.rs
@@ -138,7 +138,13 @@ impl BackingFunction {
 	pub fn get_derivative_2(&self, x: f64) -> f64 { self.derivative_2.eval(&[x]) }
 
 	/// Get string relating to the nth derivative
-	pub fn get_nth_derivative_str(&self) -> &str { &self.nth_derivative.as_ref().unwrap().2 }
+	pub fn get_nth_derivative_str(&self) -> &str {
+		&self
+			.nth_derivative
+			.as_ref()
+			.map(|a| a.2.as_str())
+			.unwrap_or("")
+	}
 
 	pub fn get_nth_derivative(&mut self, n: usize, x: f64) -> f64 {
 		match n {