From 47cbd29c27e05039f1a60778f70ae7d2cb9664dd Mon Sep 17 00:00:00 2001
From: Mark <mark@betalupi.com>
Date: Tue, 1 Aug 2023 09:43:47 -0700
Subject: [PATCH] Added detailed conversion error

---
 src/evaluate/mod.rs      | 6 +++++-
 src/evaluate/operator.rs | 8 +++++++-
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/src/evaluate/mod.rs b/src/evaluate/mod.rs
index 657d9b2..d9078b6 100644
--- a/src/evaluate/mod.rs
+++ b/src/evaluate/mod.rs
@@ -10,6 +10,7 @@ pub enum EvalError {
 	TooBig,
 	ZeroDivision,
 	IncompatibleUnit,
+	IncompatibleUnits(String, String),
 	BadDefineName,
 	Undefined(String)
 }
@@ -28,7 +29,10 @@ impl ToString for EvalError {
 				String::from("Division by zero")
 			},
 			EvalError::IncompatibleUnit => {
-				String::from("Incompatible units")
+				String::from("Incompatible unit")
+			},
+			EvalError::IncompatibleUnits(a, b) => {
+				format!("Incompatible units ({} and {})", a, b)
 			},
 			EvalError::BadDefineName => {
 				String::from("Invalid variable name")
diff --git a/src/evaluate/operator.rs b/src/evaluate/operator.rs
index 2b0798c..270c3c3 100644
--- a/src/evaluate/operator.rs
+++ b/src/evaluate/operator.rs
@@ -157,7 +157,13 @@ pub fn eval_operator(g: &Expression, context: &mut Context) -> Result<Option<Exp
 				if let Expression::Quantity(lb, vb) = b {
 					let n = va.clone().convert_to(vb.clone());
 					if n.is_none() {
-						return Err((*la + *lb + *op_loc, EvalError::IncompatibleUnit));
+						return Err((
+							*la + *lb + *op_loc,
+							EvalError::IncompatibleUnits(
+								va.convert_to_base().unit.to_string(),
+								vb.convert_to_base().unit.to_string()
+							)
+						));
 					}
 					return Ok(Some(Expression::Quantity(*la + *lb, n.unwrap())));
 				} else { return Ok(None); }