From b63a15eead7501bc365a2b7151d72c3b97bfa8d2 Mon Sep 17 00:00:00 2001
From: Raven Rothkopf <97990788+ravenrothkopf@users.noreply.github.com>
Date: Wed, 31 May 2023 11:39:56 -0400
Subject: [PATCH] add subtraction to rust interpreter (#7)

---
 crates/frontend/tests/interp.rs | 8 ++++++++
 crates/frontend/tests/sub.rose  | 1 +
 crates/interp/src/lib.rs        | 8 +++++++-
 3 files changed, 16 insertions(+), 1 deletion(-)
 create mode 100644 crates/frontend/tests/sub.rose

diff --git a/crates/frontend/tests/interp.rs b/crates/frontend/tests/interp.rs
index c648fde..1767edc 100644
--- a/crates/frontend/tests/interp.rs
+++ b/crates/frontend/tests/interp.rs
@@ -9,3 +9,11 @@ fn test_add() {
     let answer = interp(&module, Defn(0), vec![Val::F64(2.), Val::F64(2.)]);
     assert_eq!(answer, vec![Val::F64(4.)]);
 }
+
+#[test]
+fn test_sub() {
+    let src = include_str!("sub.rose");
+    let module = parse(src).unwrap();
+    let answer = interp(&module, Defn(0), vec![Val::F64(2.), Val::F64(2.)]);
+    assert_eq!(answer, vec![Val::F64(0.)]);
+}
diff --git a/crates/frontend/tests/sub.rose b/crates/frontend/tests/sub.rose
new file mode 100644
index 0000000..47b363d
--- /dev/null
+++ b/crates/frontend/tests/sub.rose
@@ -0,0 +1 @@
+def sub(x: R, y: R): R = x - y
\ No newline at end of file
diff --git a/crates/interp/src/lib.rs b/crates/interp/src/lib.rs
index 3322cb1..f3432ca 100644
--- a/crates/interp/src/lib.rs
+++ b/crates/interp/src/lib.rs
@@ -68,7 +68,13 @@ pub fn interp(module: &Module, function: Defn, args: Vec<Val>) -> Vec<Val> {
                         }
                     }
                 }
-                Binop::SubReal => todo!(),
+                Binop::SubReal => {
+                    if let Val::F64(b) = stack.pop().unwrap() {
+                        if let Val::F64(a) = stack.pop().unwrap() {
+                            stack.push(Val::F64(a - b));
+                        }
+                    }
+                }
                 Binop::MulReal => {
                     if let Val::F64(b) = stack.pop().unwrap() {
                         if let Val::F64(a) = stack.pop().unwrap() {