add hex integer literal parsing support

Cargo.toml

@@ -27,6 +27,7 @@ regex = { version = "1.5.5", optional = true}
 serde = { version = "1.0.133", optional = true}
 serde_derive = { version = "1.0.133", optional = true}
 rand = { version = "0.8.5", optional = true}
+num-traits = "0.2.15"
 
 [features]
 serde_support = ["serde", "serde_derive"]

src/token/mod.rs

@@ -348,7 +348,7 @@ fn partial_tokens_to_tokens(mut tokens: &[PartialToken]) -> EvalexprResult<Vec<T
                 },
                 PartialToken::Literal(literal) => {
                     cutoff = 1;
-                    if let Ok(number) = literal.parse::<IntType>() {
+                    if let Ok(number) = literal.parse_dec_or_hex::<IntType>() {
                         Some(Token::Int(number))
                     } else if let Ok(number) = literal.parse::<FloatType>() {
                         Some(Token::Float(number))
@@ -442,6 +442,21 @@ pub(crate) fn tokenize(string: &str) -> EvalexprResult<Vec<Token>> {
     partial_tokens_to_tokens(&str_to_partial_tokens(string)?)
 }
 
+/// Helper trait to parse strings to integer from both decimal or hex
+trait ParseDecOrHex {
+    fn parse_dec_or_hex<T: num_traits::Num>(&self) -> Result<T, T::FromStrRadixErr>;
+}
+
+impl ParseDecOrHex for str {
+    fn parse_dec_or_hex<T: num_traits::Num>(&self) -> Result<T, T::FromStrRadixErr> {
+        if self.starts_with("0x") {
+            T::from_str_radix(&self[2..], 16)
+        } else {
+            T::from_str_radix(&self, 10)
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use crate::token::{char_to_partial_token, tokenize, Token};

tests/integration.rs

@@ -2291,3 +2291,9 @@ fn test_builtin_functions_context() {
         )))
     );
 }
+
+#[test]
+fn test_hex() {
+    assert_eq!(eval("0x3"), Ok(Value::Int(3)));
+    assert_eq!(eval("0xFF"), Ok(Value::Int(255)));
+}