From 702cf74647417535ac65d37f04b3776c00adaca1 Mon Sep 17 00:00:00 2001
From: electria <elec3137+git@proton.me>
Date: Wed, 14 Oct 2026 16:50:51 -0700
Subject: [PATCH 1/2] feat: generalize splitting for plus.minus

---
 src/formatting.rs | 38 +++++++++++++++++++++++++++++---------
 1 file changed, 29 insertions(+), 9 deletions(-)

diff --git a/src/formatting.rs b/src/formatting.rs
index 7c207f5..a278c4b 100644
--- a/src/formatting.rs
+++ b/src/formatting.rs
@@ -3,15 +3,7 @@ use rug::Float;
 use crate::nodes::{self, Error};
 
 pub fn pretty_eval(input: &str, max_digits: usize) -> Result<String, Error> {
-    let (prefix, deliminator, input) = input
-        .rsplit_once('=')
-        .map(|(p, i)| (p, "= ", i))
-        .unwrap_or_else(|| {
-            input
-                .rsplit_once('&')
-                .map(|(p, i)| (p, "& ", i))
-                .unwrap_or(("", "", input))
-        });
+    let (prefix, deliminator, input) = input.rsplit_once_any(&["plus.minus ", "& ", "= "]);
 
     // no need to remove the character here,
     // as we ignore it in all other logic already
@@ -39,6 +31,26 @@ pub fn pretty_eval(input: &str, max_digits: usize) -> Result<String, Error> {
     .replace('e', " * 10^"))
 }
 
+trait StrExt {
+    fn rsplit_once_any<'a>(
+        &'a self,
+        delimiters: &[&'static str],
+    ) -> (&'a str, &'static str, &'a str);
+}
+impl StrExt for str {
+    fn rsplit_once_any<'a>(
+        &'a self,
+        delimiters: &[&'static str],
+    ) -> (&'a str, &'static str, &'a str) {
+        for delimiter in delimiters {
+            if let Some((prefix, suffix)) = self.rsplit_once(delimiter) {
+                return (prefix, delimiter, suffix);
+            }
+        }
+        return ("", "", self);
+    }
+}
+
 pub fn get_significant_digits(n: &Float) -> usize {
     let raw_string = n.to_string().replace('.', "");
 
@@ -98,6 +110,14 @@ mod tests {
         assert_eq!(pretty_eval("11.111111", 10).unwrap(), "11.111111");
     }
 
+    #[test]
+    fn plus_minus() {
+        assert_eq!(
+            pretty_eval("y & = plus.minus sqrt(15.5) \\", 10).unwrap(),
+            "y & = plus.minus 3.937003937 \\"
+        );
+    }
+
     #[test]
     fn basic_get_significant_digits() {
         let many_zeros = eval("14.00643 + 1.00784 * 4 + 35.446 + 15.9994 * 4");

From 12455924e150823ea2e340ad59db08d9720edad0 Mon Sep 17 00:00:00 2001
From: electria <elec3137+git@proton.me>
Date: Wed, 14 Oct 2026 16:52:07 -0700
Subject: [PATCH 2/2] refactor: create constant for tests

---
 src/formatting.rs | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/src/formatting.rs b/src/formatting.rs
index a278c4b..bf321bc 100644
--- a/src/formatting.rs
+++ b/src/formatting.rs
@@ -87,33 +87,34 @@ pub fn get_significant_digits(n: &Float) -> usize {
 #[cfg(test)]
 mod tests {
     use super::*;
+    const MAX_DIGITS: usize = 10;
     fn eval(s: &str) -> Float {
         crate::nodes::eval(s).unwrap()
     }
 
     #[test]
     fn character_readdition() {
-        assert_eq!(pretty_eval(" = 11", 10).unwrap(), " = 11");
-        assert_eq!(pretty_eval(" &= 11", 10).unwrap(), " &= 11");
-        assert_eq!(pretty_eval(" & 11", 10).unwrap(), " & 11");
-        assert_eq!(pretty_eval(" & 11 \\", 10).unwrap(), " & 11 \\");
+        assert_eq!(pretty_eval(" = 11", MAX_DIGITS).unwrap(), " = 11");
+        assert_eq!(pretty_eval(" &= 11", MAX_DIGITS).unwrap(), " &= 11");
+        assert_eq!(pretty_eval(" & 11", MAX_DIGITS).unwrap(), " & 11");
+        assert_eq!(pretty_eval(" & 11 \\", MAX_DIGITS).unwrap(), " & 11 \\");
     }
 
     #[test]
     fn basic_output_up_to_999() {
-        assert_eq!(pretty_eval("1", 10).unwrap(), "1");
-        assert_eq!(pretty_eval("10", 10).unwrap(), "10");
-        assert_eq!(pretty_eval("100", 10).unwrap(), "100");
-        assert_eq!(pretty_eval("999", 10).unwrap(), "999");
-        assert_eq!(pretty_eval("1000", 10).unwrap(), "1 * 10^3");
+        assert_eq!(pretty_eval("1", MAX_DIGITS).unwrap(), "1");
+        assert_eq!(pretty_eval("10", MAX_DIGITS).unwrap(), "10");
+        assert_eq!(pretty_eval("100", MAX_DIGITS).unwrap(), "100");
+        assert_eq!(pretty_eval("999", MAX_DIGITS).unwrap(), "999");
+        assert_eq!(pretty_eval("1000", MAX_DIGITS).unwrap(), "1 * 10^3");
 
-        assert_eq!(pretty_eval("11.111111", 10).unwrap(), "11.111111");
+        assert_eq!(pretty_eval("11.111111", MAX_DIGITS).unwrap(), "11.111111");
     }
 
     #[test]
     fn plus_minus() {
         assert_eq!(
-            pretty_eval("y & = plus.minus sqrt(15.5) \\", 10).unwrap(),
+            pretty_eval("y & = plus.minus sqrt(15.5) \\", MAX_DIGITS).unwrap(),
             "y & = plus.minus 3.937003937 \\"
         );
     }