Documentation and report.

lisp.py

@@ -1,20 +1,11 @@
 import math
-import string
 from functools import reduce
 
-def prettyprint(expression) -> str:
-	if type(expression) is list:
-		retvalue = "("
-		for x in expression:
-			retvalue += prettyprint(x) + " "
-		return retvalue.rstrip() + ")"
-	elif type(expression) is bool:
-		return "T" if expression else "NIL"
-	elif str():
-		return expression.upper()
-	else:
-		return str(expression)
-
+### LISP.PY
+### Autumn Wolf
+### 04/26/26
+### CSE3024
+#	This file (and contained class) handles lisp interpreter details, environment management, and expression evaluation.
 
 class Function:
 	def __init__(self, parameters, expression):
@@ -28,11 +19,15 @@ class Lisp:
 		else:
 			self.env = env
 
+	# Recursively evaluate an expression
 	def evaluate(self, expression):
+		# Handle literals
 		if type(expression) is not list:
 			if expression in self.env.keys():
 				return self.env[expression]
 			return expression
+
+		# Handling of some special operations
 		operation = expression[0]
 		if type(operation) is list:
 			operation = self.evaluate(operation)
@@ -41,7 +36,7 @@ class Lisp:
 		if operation == "QUOTE":
 			return expression[1:][0]
 		if operation != "DEFUN":
-			arguments = [self.evaluate(x) for x in expression[1:]]
+			arguments = [self.evaluate(x) for x in expression[1:]] # Don't evaluate for defun or quote!
 		else:
 			arguments = expression[1:]
 		match operation:
@@ -53,6 +48,7 @@ class Lisp:
 				return reduce(lambda x,y: x*y, arguments)
 			case "/":
 				return reduce(lambda x,y: x/y, arguments)
+
 			case "CAR":
 				if len(arguments) != 1:
 					raise ValueError("Expected 1 argument")
@@ -68,6 +64,7 @@ class Lisp:
 					return [arguments[0]]+arguments[1]
 				else:
 					return [arguments[0]]+arguments[1]
+
 			case "SQRT":
 				if len(arguments) != 1:
 					raise ValueError("Expected 1 argument")
@@ -76,6 +73,7 @@ class Lisp:
 				if len(arguments) != 2:
 					raise ValueError("Expected 2 arguments")
 				return pow(arguments[0], arguments[1])
+
 			case "IF":
 				if len(arguments) != 3:
 					raise ValueError("Expected 3 arguments")
@@ -111,9 +109,11 @@ class Lisp:
 				if len(arguments) != 1:
 					raise ValueError("Expected 1 argument")
 				return not arguments[0]
+
 			case "QUIT":
 				print(">> bye")
 				raise SystemExit
+
 			case "DEFINE":
 				if len(arguments) != 2:
 					raise ValueError("Expected 2 arguments")
@@ -132,6 +132,7 @@ class Lisp:
 				else:
 					raise ValueError("Undefined variable: " + str(arguments[0]))
 				return arguments[0]
+
 			case "MAPCAR":
 				if len(arguments) != 3:
 					raise ValueError("Expected 3 arguments")
@@ -140,14 +141,14 @@ class Lisp:
 					result.append(self.evaluate([arguments[0], arguments[1][i], arguments[2][i]]))
 				return result
 			case _:
-				if operation in self.env.keys():
+				if operation in self.env.keys(): # Check for user-defined functions
 					if type(self.env[operation]) == Function:
 						func = self.env[operation]
 						functionrunner = Lisp(self.env)
 						if len(arguments) != len(func.parameters):
 							raise ValueError("Expected " + str(len(func.parameters)) + " arguments")
 						for i in range(0, len(arguments)):
-							functionrunner.env[func.parameters[i]] = arguments[i]
+							functionrunner.env[func.parameters[i]] = arguments[i] # Populate sub-interpreter environment
 						return functionrunner.evaluate(self.env[operation].expression)
 					else:
 						raise TypeError("This value is not a valid function: " + operation)