Ignoring operators at the end (with option to disable)

src/lexer.rs

@@ -9,9 +9,19 @@ use crate::LexerKeyword::{In, PercentChar, Per, Mercury, Hg, PoundForce, PoundWo
 use crate::FunctionIdentifier::{Cbrt, Ceil, Cos, Exp, Abs, Floor, Ln, Log, Round, Sin, Sqrt, Tan};
 use crate::units::Unit::*;
 
-pub fn lex(input: &str) -> Result<TokenVector, String> {
+pub fn lex(input: &str, allow_trailing_operators: bool) -> Result<TokenVector, String> {
+
+  let mut input = input.replace(",", ""); // ignore commas
+
+  if allow_trailing_operators {
+    match &input.chars().last().unwrap_or('x') {
+      '+' | '-' | '*' | '/' | '%' | '^' | '(' => {
+        input.pop();
+      },
+      _ => {},
+    }
+  }
 
-  let input = input.replace(",", "");
   let mut chars = input.chars().peekable();
   let mut tokens: TokenVector = vec![];
   let max_word_length = 30;

src/main.rs

@@ -88,14 +88,20 @@ mod evaluator;
 mod lookup;
 
 fn main() {
-  
   use std::env;
   let args: Vec<String> = env::args().collect();
-  let s = if args.len() >= 2 { &args[1] } else { "0.1" };
+  if args.len() >= 2 {
+    eval(&args[1], true);
+  } else {
+    println!("No argument supplied");
+  }
+}
+
+pub fn eval(input: &str, allow_trailing_operators: bool) {
 
   let lex_start = Instant::now();
   
-  match lexer::lex(s) {
+  match lexer::lex(input, allow_trailing_operators) {
     Ok(tokens) => {
       let lex_time = Instant::now().duration_since(lex_start).as_nanos() as f32;