daisy · NSoiffer · Jan 8, 2026 · Jan 7, 2026
diff --git a/src/braille.rs b/src/braille.rs
@@ -3079,7 +3079,7 @@ mod tests {
             </mrow>
         </math>";
         crate::interface::set_rules_dir(super::super::abs_rules_dir_path()).unwrap();
-        set_mathml(mathml_str.to_string()).unwrap();
+        set_mathml(mathml_str).unwrap();
         set_preference("BrailleCode", "UEB").unwrap();
         set_preference("BrailleNavHighlight", "All").unwrap();
         let braille = get_braille("id-2")?;
@@ -3135,7 +3135,7 @@ mod tests {
         </mrow>
        </math>";
         crate::interface::set_rules_dir(super::super::abs_rules_dir_path()).unwrap();
-        set_mathml(mathml_str.to_string()).unwrap();
+        set_mathml(mathml_str).unwrap();
         set_preference("BrailleNavHighlight", "Off").unwrap();
 
         set_preference("BrailleCode", "Nemeth").unwrap();
@@ -3187,7 +3187,7 @@ mod tests {
     fn test_UEB_start_mode() -> Result<()> {
         let mathml_str = "<math><msup><mi>x</mi><mi>n</mi></msup></math>";
         crate::interface::set_rules_dir(super::super::abs_rules_dir_path()).unwrap();
-        set_mathml(mathml_str.to_string()).unwrap();
+        set_mathml(mathml_str).unwrap();
         set_preference("BrailleCode", "UEB").unwrap();
         set_preference("UEB_START_MODE", "Grade2").unwrap();
         let braille = get_braille("")?;

diff --git a/src/interface.rs b/src/interface.rs
@@ -66,17 +66,14 @@ fn init_mathml_instance() -> RefCell<Package> {
 
 /// Set the Rules directory
 /// IMPORTANT: this should be the very first call to MathCAT. If 'dir' is an empty string, the environment var 'MathCATRulesDir' is tried.
-pub fn set_rules_dir(dir: String) -> Result<()> {
+pub fn set_rules_dir(dir: impl AsRef<str>) -> Result<()> {
     enable_logs();
     use std::path::PathBuf;
+    let dir = dir.as_ref();
     let dir = if dir.is_empty() {
-        std::env::var_os("MathCATRulesDir")
-            .unwrap_or_default()
-            .to_str()
-            .unwrap()
-            .to_string()
+        std::env::var_os("MathCATRulesDir").unwrap_or_default()
     } else {
-        dir
+        std::ffi::OsString::from(dir)
     };
     let pref_manager = crate::prefs::PreferenceManager::get();
     return pref_manager.borrow_mut().initialize(PathBuf::from(dir));
@@ -92,7 +89,7 @@ pub fn get_version() -> String {
 /// This will override any previous MathML that was set.
 /// This returns canonical MathML with 'id's set on any node that doesn't have an id.
 /// The ids can be used for sync highlighting if the `Bookmark` API preference is true.
-pub fn set_mathml(mathml_str: String) -> Result<String> {
+pub fn set_mathml(mathml_str: impl AsRef<str>) -> Result<String> {
     enable_logs();
     lazy_static! {
         // if these are present when resent to MathJaX, MathJaX crashes (https://github.com/mathjax/MathJax/issues/2822)
@@ -111,6 +108,7 @@ pub fn set_mathml(mathml_str: String) -> Result<String> {
     // This call reads all of them for the current preferences, but that's ok since they will likely be used
     crate::speech::SPEECH_RULES.with(|rules| rules.borrow_mut().read_files())?;
 
+    let mathml_str = mathml_str.as_ref();
     return MATHML_INSTANCE.with(|old_package| {
         static HTML_ENTITIES_MAPPING: phf::Map<&str, &str> = include!("entities.in");
 
@@ -535,10 +533,10 @@ pub fn get_supported_languages() -> Vec<String> {
     return language_paths;
  }
 
- pub fn get_supported_speech_styles(lang: String) -> Vec<String> {
+ pub fn get_supported_speech_styles(lang: impl AsRef<str>) -> Vec<String> {
     enable_logs();
     let rules_dir = crate::prefs::PreferenceManager::get().borrow().get_rules_dir();
-    let lang_dir = rules_dir.join("Languages").join(lang);
+    let lang_dir = rules_dir.join("Languages").join(lang.as_ref());
     let mut speech_styles = find_files_in_dir_that_ends_with_shim(&lang_dir, "_Rules.yaml");
     for file_name in &mut speech_styles {
         file_name.truncate(file_name.len() - "_Rules.yaml".len())
@@ -1103,9 +1101,9 @@ mod tests {
         // this forces initialization
         set_rules_dir(super::super::abs_rules_dir_path()).unwrap();
 
-        let entity_str = set_mathml("<math><mrow><mo>&minus;</mo><mi>&mopf;</mi></mrow></math>".to_string()).unwrap();
+        let entity_str = set_mathml("<math><mrow><mo>&minus;</mo><mi>&mopf;</mi></mrow></math>").unwrap();
         let converted_str =
-            set_mathml("<math><mrow><mo>&#x02212;</mo><mi>&#x1D55E;</mi></mrow></math>".to_string()).unwrap();
+            set_mathml("<math><mrow><mo>&#x02212;</mo><mi>&#x1D55E;</mi></mrow></math>").unwrap();
 
         // need to remove unique ids
         lazy_static! {
@@ -1116,19 +1114,19 @@ mod tests {
         assert_eq!(entity_str, converted_str, "normal entity test failed");
 
         let entity_str = set_mathml(
-            "<math data-quot=\"&quot;value&quot;\" data-apos='&apos;value&apos;'><mi>XXX</mi></math>".to_string(),
+            "<math data-quot=\"&quot;value&quot;\" data-apos='&apos;value&apos;'><mi>XXX</mi></math>",
         )
         .unwrap();
         let converted_str =
-            set_mathml("<math data-quot='\"value\"' data-apos=\"'value'\"><mi>XXX</mi></math>".to_string()).unwrap();
+            set_mathml("<math data-quot='\"value\"' data-apos=\"'value'\"><mi>XXX</mi></math>").unwrap();
         let entity_str = ID_MATCH.replace_all(&entity_str, "");
         let converted_str = ID_MATCH.replace_all(&converted_str, "");
         assert_eq!(entity_str, converted_str, "special entities quote test failed");
 
         let entity_str =
-            set_mathml("<math><mo>&lt;</mo><mo>&gt;</mo><mtext>&amp;lt;</mtext></math>".to_string()).unwrap();
+            set_mathml("<math><mo>&lt;</mo><mo>&gt;</mo><mtext>&amp;lt;</mtext></math>").unwrap();
         let converted_str =
-            set_mathml("<math><mo>&#x003C;</mo><mo>&#x003E;</mo><mtext>&#x0026;lt;</mtext></math>".to_string())
+            set_mathml("<math><mo>&#x003C;</mo><mo>&#x003E;</mo><mtext>&#x0026;lt;</mtext></math>")
                 .unwrap();
         let entity_str = ID_MATCH.replace_all(&entity_str, "");
         let converted_str = ID_MATCH.replace_all(&converted_str, "");
@@ -1140,13 +1138,13 @@ mod tests {
         use std::env;
         // MathCAT will check the env var "MathCATRulesDir" as an override, so the following test might succeed if we don't override the env var
         env::set_var("MathCATRulesDir", "MathCATRulesDir");
-        assert!(set_rules_dir("someInvalidRulesDir".to_string()).is_err());
+        assert!(set_rules_dir("someInvalidRulesDir").is_err());
         assert!(
             set_rules_dir(super::super::abs_rules_dir_path()).is_ok(),
             "\nset_rules_dir to '{}' failed",
             super::super::abs_rules_dir_path()
         );
-        assert!(set_mathml("<math><mn>1</mn></math>".to_string()).is_ok());
+        assert!(set_mathml("<math><mn>1</mn></math>").is_ok());
     }
 
     #[test]

diff --git a/src/main.rs b/src/main.rs
@@ -224,11 +224,11 @@ fn main() {
   set_preference("Bookmark", "false").unwrap();
   set_preference("SpeechStyle", "ClearSpeak").unwrap();
   info!("Languages: {}", libmathcat::interface::get_supported_languages().join(", "));
-  info!("Speech styles: {}", libmathcat::interface::get_supported_speech_styles("ClearSpeak".to_string()).join(", "));
+  info!("Speech styles: {}", libmathcat::interface::get_supported_speech_styles("ClearSpeak").join(", "));
   info!("BrailleCodes: {}", libmathcat::interface::get_supported_braille_codes().join(", "));
   // set_preference("DecimalSeparators", ",").unwrap();
   // set_preference("BlockSeparators", ". ").unwrap();
-  if let Err(e) = set_mathml(expr.to_string()) {
+  if let Err(e) = set_mathml(expr) {
     panic!("Error: exiting -- {}", errors_to_string(&e));
   };
 
@@ -308,7 +308,7 @@ fn timing_test(expr: &str, n_loops: usize) {
   let n_loops_float = n_loops as f64;
   let instant = Instant::now();
   for _ in 0..n_loops {
-    if let Err(e) = set_mathml(expr.to_string()) {
+    if let Err(e) = set_mathml(expr) {
       panic!("Error: exiting -- {}", errors_to_string(&e));
     };
     match get_spoken_text() {
@@ -324,7 +324,7 @@ fn timing_test(expr: &str, n_loops: usize) {
 
   let instant = Instant::now();
   for _ in 0..n_loops {
-    if let Err(e) = set_mathml(expr.to_string()) {
+    if let Err(e) = set_mathml(expr) {
       panic!("Error: exiting -- {}", errors_to_string(&e));
     };
   }
@@ -350,7 +350,7 @@ fn timing_test(expr: &str, n_loops: usize) {
   }
   info!("Time taken (time for {} braille averaged over {} loops): {}ms", get_preference("BrailleCode").unwrap(), n_loops, instant.elapsed().as_millis() as f64/n_loops_float);
 
-    if let Err(e) = set_mathml(expr.to_string()) {
+    if let Err(e) = set_mathml(expr) {
       panic!("Error: exiting -- {}", errors_to_string(&e));
     };
   set_preference("BrailleCode", "Nemeth").unwrap();

diff --git a/src/navigate.rs b/src/navigate.rs
@@ -1025,7 +1025,7 @@ mod tests {
         set_preference("SpeechStyle", "SimpleSpeak").unwrap();
         set_preference("Verbosity", "Medium").unwrap();
         set_preference("Overview", "False").unwrap();
-        set_mathml(mathml.to_string()).unwrap();
+        set_mathml(mathml).unwrap();
     }
 
     #[test]

diff --git a/src/prefs.rs b/src/prefs.rs
@@ -1165,7 +1165,7 @@ cfg_if::cfg_if! {if #[cfg(not(feature = "include-zip"))] {
             assert_eq!(&pref_manager.pref_to_string("SpeechStyle"), "ClearSpeak");
             assert_eq!(rel_path(&pref_manager.rules_dir, pref_manager.speech.as_path()), PathBuf::from("Languages/zz/ClearSpeak_Rules.yaml"));
         });
-        interface::set_mathml("<math><mo>+</mo><mn>10</mn></math>".to_string()).unwrap();
+        interface::set_mathml("<math><mo>+</mo><mn>10</mn></math>").unwrap();
         assert_eq!(interface::get_spoken_text().unwrap(), "ClearSpeak positive from zz 10");
 
         let mut file_path = PathBuf::default();

diff --git a/src/shim_filesystem.rs b/src/shim_filesystem.rs
@@ -274,7 +274,7 @@ cfg_if! {
             // file_name should be path name starting at Rules dir: e.g, "Rules/en/navigate.yaml"
             OVERRIDE_FILE_NAME.with(|name| *name.borrow_mut() = file_name.to_string().replace("/", "\\"));
             OVERRIDE_FILE_CONTENTS.with(|contents| *contents.borrow_mut() = file_contents.to_string());
-            crate::interface::set_rules_dir("Rules".to_string()).unwrap();       // force reinitialization after the change
+            crate::interface::set_rules_dir("Rules").unwrap();       // force reinitialization after the change
         }
     } else {
         pub fn is_file_shim(path: &Path) -> bool {

diff --git a/src/speech.rs b/src/speech.rs
@@ -2887,7 +2887,7 @@ cfg_if::cfg_if! {if #[cfg(not(feature = "include-zip"))] {
         set_rules_dir(super::super::abs_rules_dir_path()).unwrap();
         set_preference("Language", "zz-aa").unwrap();
         // not much is support in zz
-        if let Err(e) = set_mathml("<math><mi>x</mi></math>".to_string()) {
+        if let Err(e) = set_mathml("<math><mi>x</mi></math>") {
             error!("{}", crate::errors_to_string(&e));
             panic!("Should not be an error in setting MathML")
         }

diff --git a/tests/braille/Nemeth/other.rs b/tests/braille/Nemeth/other.rs
@@ -81,7 +81,7 @@ fn find_baseline_indicator_bug_364() {
     set_rules_dir(abs_rules_dir_path()).unwrap();
     set_preference("BrailleNavHighlight", "Off").unwrap();
     set_preference("BrailleCode", "Nemeth").unwrap();
-    if let Err(e) = set_mathml(expr.to_string()) {
+    if let Err(e) = set_mathml(expr) {
         panic!("{}", errors_to_string(&e));
     };
     match get_navigation_node_from_braille_position(4) {

diff --git a/tests/common/mod.rs b/tests/common/mod.rs
@@ -43,7 +43,7 @@ fn strip_spaces(str: &str) -> String {
 
 #[allow(dead_code)]     // used in testing
 fn check_answer(test: &str, target: &str, failure_message: &str) {
-    if let Err(e) = set_mathml(test.to_string()) {
+    if let Err(e) = set_mathml(test) {
         panic!("{}", errors_to_string(&e));
     };
     match get_spoken_text() {
@@ -123,7 +123,7 @@ pub fn test_braille(code: &str, mathml: &str, braille: &str) {
         "CMU" => set_preference("Language", "es").unwrap(),
         "UEB" | "Nemeth" | _ => set_preference("Language", "en").unwrap(),
     }
-    if let Err(e) = set_mathml(mathml.to_string()) {
+    if let Err(e) = set_mathml(mathml) {
         panic!("{}", errors_to_string(&e));
     };
     match get_braille("") {
@@ -151,7 +151,7 @@ pub fn test_braille_prefs(code: &str, test_prefs: Vec<(&str, &str)>, mathml: &st
         set_preference(pref_name, pref_value).unwrap();
     };
 
-    if let Err(e) = set_mathml(mathml.to_string()) {
+    if let Err(e) = set_mathml(mathml) {
         panic!("{}", errors_to_string(&e));
     };
     match get_braille("") {
@@ -240,7 +240,7 @@ pub fn test_from_braille(code: &str, mathml: &str, braille: &str) {
         "CMU" => set_preference("Language", "es").unwrap(),
         "UEB" | "Nemeth" | _ => set_preference("Language", "en").unwrap(),
     }
-    if let Err(e) = set_mathml(mathml.to_string()) {
+    if let Err(e) = set_mathml(mathml) {
         panic!("{}", errors_to_string(&e));
     };