diff --git a/runner.py b/runner.py
new file mode 100644
index 0000000..dff6efe
--- /dev/null
+++ b/runner.py
@@ -0,0 +1,46 @@
+import tokens
+from parser import Parser
+
+class Runner:
+	def __init__(self):
+		self.macro_table = {}
+		self.expr = None
+
+	# Apply a list of definitions
+	def run(self, line: str):
+		e = Parser.parse_line(line)
+
+		if isinstance(e, tokens.macro_expression):
+			if e.label in self.macro_table:
+				raise NameError(f"Label {e.label} exists!")
+			e.exp.bind_variables()
+			self.macro_table[e.label] = e.exp
+
+		elif isinstance(e, tokens.command):
+			pass
+		else:
+			e.bind_variables()
+			self.expr = e
+
+			outs = [str(e)]
+			for i in range(300):
+				r = self.expr.reduce(self.macro_table)
+				self.expr = r.output
+				s = str(r.output)
+				p = s if len(s) < 100 else s[:97] + "..."
+
+				#if s in outs:
+					#print(p)
+					#print("\nLoop detected, exiting.")
+					#break
+
+				if not r.was_reduced:
+					print("\nCannot evaluate any further.")
+					break
+
+			print(f"Performed {i} {'operations' if i != 1 else 'operation'}.")
+			return self.expr
+
+	def run_lines(self, lines):
+		for l in lines:
+			self.run(l)