added sort and median helper functions

src/context/helper.rs

@@ -158,11 +158,33 @@ pub fn average(arg: &Value) -> EvalResult {
 			total +=
 				if		let Value::Float(float) = arg { float.clone() }
 				else if	let Value::Int(int)		= arg { int.clone() as f64 }
-				else { todo!() };
+				else { return Err(EvalexprError::expected_number(arg.clone())) };
 		}
 
 		Ok( (total / len).into() )
-	} else { todo!() }
+	} else { Err(EvalexprError::expected_tuple(arg.clone())) }
+}
+
+pub fn median(arg: &Value) -> EvalResult {
+	if arg.is_tuple() {
+		let args = sort(arg).unwrap().as_tuple().unwrap();
+		let len = args.len();
+		let middle = len / 2;
+		if len % 2 != 0 { Ok(args[middle].as_number().unwrap().into()) }
+		else {
+			let left = args[middle - 1].as_number().unwrap();
+			let right = args[middle].as_number().unwrap();
+			Ok( ((left + right) / 2f64 ).into() )
+		}
+	} else { Err(EvalexprError::expected_tuple(arg.clone())) }
+}
+
+pub fn sort(arg: &Value) -> EvalResult {
+	if let Value::Tuple(args) = arg {
+		let mut args = args.clone();
+		args.sort_by(|a, b| a.as_number().unwrap().total_cmp(&b.as_number().unwrap()));
+		Ok(args.into())
+	} else { Err(EvalexprError::expected_tuple(arg.clone())) }
 }
 
 //	Radix conversion

src/context/mod.rs

@@ -38,6 +38,8 @@ pub fn build(args: &mut Arguments) -> HashMapContext {
 
 				//	data science functions
 				"avg"	=>	Function::new(|arg| helper::average(arg)),
+				"med"	=>	Function::new(|arg| helper::median(arg)),
+				"sort"	=>	Function::new(|arg| helper::sort(arg)),
 
 				//	radix functions
 				"bin"	=>	Function::new(|arg| helper::binary(arg)),