From dcf8a50f340e5710d3bf0d262b983bb0fbe0a7a0 Mon Sep 17 00:00:00 2001
From: Garritt McCune <glmccune@gmail.com>
Date: Sun, 26 Apr 2020 18:17:40 -0500
Subject: [PATCH] Added support for negative variables in the tokenizer and
 ptoken object.

---
 calc_engine.py |  1 -
 ptoken.py      |  3 ++-
 tokenizer.py   | 24 ++++++++++++++++++------
 3 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/calc_engine.py b/calc_engine.py
index a2930b8..28364e5 100644
--- a/calc_engine.py
+++ b/calc_engine.py
@@ -6,7 +6,6 @@ from collections import deque
 debug = False
 
 def calculate_results(tokens):
-	tokenizer.print_token_list(tokens)
 	return process_tokens(convert_to_deque(tokens), True)
 	
 def process_tokens(tokens, top_level = False):
diff --git a/ptoken.py b/ptoken.py
index 6cd5292..ae4187c 100755
--- a/ptoken.py
+++ b/ptoken.py
@@ -1,7 +1,8 @@
 class Token:
-	def __init__(self, value, type):
+	def __init__(self, value, type, is_negative_variable = False):
 		self.value = value
 		self.type = type
+		self.is_negative_variable = is_negative_variable
 
 class TokenType:
 	add = 0
diff --git a/tokenizer.py b/tokenizer.py
index 7c58c19..8e6c30f 100644
--- a/tokenizer.py
+++ b/tokenizer.py
@@ -9,6 +9,7 @@ def get_tokens_from_expression_string(expression_string):
 	tmp = ""
 	parsing_number = False
 	symbols_dic = {}  # Dictionary to keep track of the no. of times each variable appears.
+	variable_is_negative = False
 
 	for i in range(0, len(expression_string)):
 		c = expression_string[i]
@@ -26,8 +27,7 @@ def get_tokens_from_expression_string(expression_string):
 			continue
 		
 		elif c == '-' and not parsing_number:
-			if expression_string[i + 1] == '.' or expression_string[i + 1].isdigit():
-				print(tokens[-1].value)
+			if expression_string[i + 1] == '.' or expression_string[i + 1].isdigit():				
 				if token.TokenType.get_operator(tokens[-1].value) != token.TokenType.unknown:#tokens[-1].type == token.TokenType
 					#print(tokens[-1].value)
 					#tokens.append(token.Token('+', token.TokenType.add))
@@ -40,6 +40,10 @@ def get_tokens_from_expression_string(expression_string):
 					tokens.append(token.Token(c, token.TokenType.get_operator(c)))
 					parsing_number = False
 					tmp = ""
+			elif expression_string[i + 1].isalpha():
+				#Must be a variable.
+				if tokens[-1].type == token.TokenType.exp_start:
+					variable_is_negative = True
 			else:
 				tokens.append(token.Token(c, token.TokenType.get_operator(c)))
 				parsing_number = False
@@ -71,7 +75,7 @@ def get_tokens_from_expression_string(expression_string):
 			if len(tokens) > 1:
 				lookBehind = tokens[-1]
 				if lookBehind.type == token.TokenType.exp_end:
-					tokens.append(token.Token("^", token.TokenType.power))
+					tokens.append(token.Token("^", token.TokenType.power))					
 					
 			if (i + 1) < len(expression_string):
 				lookAHead = expression_string[i + 1]
@@ -88,7 +92,8 @@ def get_tokens_from_expression_string(expression_string):
 				symbols_dic[c] += 1
 			else:
 				symbols_dic[c] = 1
-			tokens.append(token.Token(c + str(symbols_dic[c]), token.TokenType.variable))
+			tokens.append(token.Token(c + str(symbols_dic[c]), token.TokenType.variable, variable_is_negative))
+			variable_is_negative = False
 			parsing_number = False
 			tmp = ""
 	
@@ -104,7 +109,10 @@ def replace_variables(tokens, new_constants):
 	newTokenList = []
 	for t in tokens:
 		if t.type == token.TokenType.variable:
-			newTokenList.append(token.Token(new_constants.pop(0), token.TokenType.constant))
+			if not t.is_negative_variable:
+				newTokenList.append(token.Token(new_constants.pop(0), token.TokenType.constant))
+			else:
+				newTokenList.append(token.Token(new_constants.pop(0) * -1, token.TokenType.constant))
 		else:
 			newTokenList.append(token.Token(t.value, t.type))
 			
@@ -112,7 +120,11 @@ def replace_variables(tokens, new_constants):
 	
 def print_token_list(tokens):
 	for tk in tokens:
-		print("%s " %(tk.value), end = "")#, token.TokenType.get_token_type_name(tk.type)), end = "")
+		if tk.type == token.TokenType.variable:
+			if tk.is_negative_variable:
+				print("-%s " %(tk.value), end = "")
+		else:
+			print("%s " %(tk.value), end = "")
 	print()
 	
 def stringify_token_list(tokens):