rpn(1): fixed exiting the program on EOF

src/rpn.rs

@@ -57,7 +57,7 @@ extern crate sysexits;
 use sysexits::EX_DATAERR;
 
 #[derive(Clone, Copy, PartialEq, PartialOrd, Debug)]
-/// enum CalcType is a type containing operations used in the calculator.
+// enum CalcType is a type containing operations used in the calculator.
 enum CalcType {
 	Add,
 	Subtract,
@@ -78,7 +78,7 @@ impl fmt::Display for EvaluationError {
 	}
 }
 
-/// str_to_calc_type converts a string to an optional `CalcType`.
+// str_to_calc_type converts a string to an optional `CalcType`.
 fn str_to_calc_type(string: &str) -> Option<CalcType> {
 	let as_int = string.parse::<f64>();
 	let result = match as_int {
@@ -105,6 +105,12 @@ fn eval(
 	initial_stack: VecDeque<f64>,
 ) -> Result<VecDeque<f64>, EvaluationError> {
 	let mut stack = initial_stack;
+
+	if input.is_empty() {
+		stack.clear();
+		return Ok(stack);
+	}
+
 	// Split the input into tokens.
 	let toks = input.split(' ').collect::<Vec<&str>>();
 	let mut ops: VecDeque<CalcType> = VecDeque::new();
@@ -185,12 +191,15 @@ fn main() -> ExitCode {
 	if argv.get(1).is_none() {
 		while let Ok(_) = stdin().read_line(&mut buf) {
 			match eval(&buf.trim(), stack) {
-				Ok(val) => {
-					stack = val.clone();
-					let precise = round_precise(
-						stack.iter().last().unwrap(),
-						precision,
-					);
+				Ok(s) => {
+					stack = s.clone();
+
+					let val = match stack.iter().last() {
+						Some(v) => v,
+						None => break,
+					};
+
+					let precise = round_precise(val, precision);
 					println!("{}", precise.to_string());
 					buf.clear();
 				},