Freak out instead of ignoring unexpected arguments

CHANGELOG.md

@@ -1,3 +1,8 @@
+## Next
+- Freak out instead of ignoring unexpected arguments
+- Add support for non-US "metre" and "litre" spellings
+- Fix decimeter parsed as centimeter
+
 ## 1.5.1 - 2021 Jun 10
 - Fix numbers unnecessarily displayed in E notation
 

src/main.rs

@@ -1,27 +1,44 @@
 use cpc::eval;
 use cpc::units::Unit;
+use std::process::exit;
 
-/// cpc CLI interface
+/// CLI interface
 fn main() {
   use std::env;
-  let mut args: Vec<String> = env::args().collect();
+  let mut args = env::args().into_iter();
+  args.next();
   let mut verbose = false;
-  if let Some(pos) = args.iter().position(|x| x == "-v" || x == "--verbose") {
-    verbose = true;
-    args.remove(pos);
+  let mut expression_opt = None;
+  for arg in args {
+    match arg.as_str() {
+      "-v" | "--verbose" => verbose = true,
+      _ => {
+        if expression_opt == None {
+          expression_opt = Some(arg);
+        } else {
+          eprintln!("Unexpected argument: {}", arg);
+          exit(1);
         }
-  if args.len() >= 2 {
-    match eval(&args[1], true, Unit::Celsius, verbose) {
+      }
+    }
+  }
+  match expression_opt {
+    Some(expression) => {
+      match eval(&expression, true, Unit::Celsius, verbose) {
         Ok(answer) => {
           if !verbose {
             println!("{}", answer);
           }
         },
         Err(e) => {
-        println!("{}", e)
+          eprintln!("{}", e);
+          exit(1);
         },
       }
-  } else {
+    }
+    None => {
       eprintln!("No argument supplied");
+      exit(1);
+    }
   }
 }