feat: generalize splitting for plus.minus

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");