From 6454c537c2c714b2fcb2d0260bf12e6cf6675d77 Mon Sep 17 00:00:00 2001
From: Varmen8 <Varmen8@users.noreply.github.com>
Date: Wed, 27 Jun 2018 23:04:58 +0200
Subject: [PATCH] Add polynomial subtraction

---
 main.py | 63 ++++++++++++++++++++++++++++++++++++++++++---------------
 1 file changed, 47 insertions(+), 16 deletions(-)

diff --git a/main.py b/main.py
index d0f033f..adff4ae 100644
--- a/main.py
+++ b/main.py
@@ -33,8 +33,7 @@ class Poly:
 
     def __mul__(self, other):
 
-        if self.int_mod != other.int_mod:
-            raise Exception("Different modulo")
+        assert self.int_mod == other.int_mod
 
         elements = {}
 
@@ -63,8 +62,7 @@ class Poly:
 
     def __add__(self, other):
 
-        if self.int_mod != other.int_mod:
-            raise Exception("Different modulo")
+        assert self.int_mod == other.int_mod
 
         elements = self.elements.copy()
 
@@ -74,8 +72,29 @@ class Poly:
             else:
                 elements[f] = other.elements[f]
 
-        return Poly(self.int_mod,
-                    list(reversed(list(sorted(elements.values())))))
+        els = {}
+        for i in reversed(range(len(elements))):
+            els[f"x{i}"] = elements[f"x{i}"]
+
+        return Poly(self.int_mod, list(reversed(list(els.values()))))
+
+    def __sub__(self, other):
+
+        assert self.int_mod == other.int_mod
+
+        elements = self.elements.copy()
+
+        for e in other.elements:
+            if e in elements:
+                elements[e] -= other.elements[e]
+            else:
+                elements[e] = -other.elements[e]
+
+        els = {}
+        for i in reversed(range(len(elements))):
+            els[f"x{i}"] = elements[f"x{i}"]
+
+        return Poly(self.int_mod, list(reversed(list(els.values()))))
 
     def __truediv__(self, other):
 
@@ -134,24 +153,36 @@ if __name__ == "__main__":
     # print(c.elements)
     # print(c)
     # print(p ** 2)
-    d = Poly(5, [-3, 1])
+
     # print(p)
     # print(d)
     # print(p)
     # print(p + d)
-
+    d = Poly(5, [-3, 1])
     g = Poly(5, [1, 2, 1])
+    print(d)
+    print(g)
+    print()
+
     # print()
     # print(g ** 2)
-    print(d)
-    print(g)
-    # c = d * g
-    print(g * d)
-    print(d * g)
-    print(g + d)
+    # print(d)
+    # print(g)
+    # # c = d * g
+    # print(g * d)
+    # print(d * g)
+    # print(g + d)
+    # print(d + g)
+    # print(d)
+    # print(g)
+    print(g - d)
+    print(d - g)
+
+    print()
     print(d + g)
-    print(d)
-    print(g)
+    print(g + d)
+    # print(d)
+    # print(g)
     # print(g - d)
     # print(p / d)
     # print(p.elements[0])