1 files changed, 32 insertions, 0 deletions
diff --git a/projects/hack-vm/compare.py b/projects/hack-vm/compare.py
new file mode 100644
index 0000000..1565b11
--- /dev/null
+++ b/projects/hack-vm/compare.py
@@ -0,0 +1,32 @@
+from .utils import *
+
+# template for lt, gt, and eq
+COMPARE_ASM = """@SP
+AM=M-1
+D=M
+A=A-1
+D=M-D
+M=0
+@END_{tag}
+D;{jmp}
+@SP
+A=M-1
+M=-1
+(END_{tag})
+"""
+
+# exact complement of VM command which leaves top of stack false
+JMP = {
+    "lt": "JGE",
+    "eq": "JNE",
+    "gt": "JLE",
+}
+
+tag_idx = 0
+
+
+def translate_compare(command):
+    global tag_idx
+    asm = COMPARE_ASM.format(tag=f"{command.upper()}_{tag_idx}", jmp=JMP[command])
+    tag_idx += 1
+    return asm