From 18de900a38f2d06da4265175b512dd2648939c61 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20M=C3=BCller?= <stefan.mueller@aksdb.de>
Date: Mon, 20 May 2024 00:56:22 +0200
Subject: [PATCH 1/3] Fixed BigInt subtraction for equal operands

---
 UBigInt.pas | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/UBigInt.pas b/UBigInt.pas
index a49ea16..4c8505e 100644
--- a/UBigInt.pas
+++ b/UBigInt.pas
@@ -237,10 +237,17 @@ class function TBigInt.SubtractAbsoluteValues(constref AA, AB: TBigInt; const AR
 var
   a, b: TBigInt;
   carry: Cardinal;
-  i, j, lastNonZeroDigitIndex, len: Integer;
+  compare, i, j, lastNonZeroDigitIndex, len: Integer;
 begin
   // Establishes the operand order, such that Abs(a) is not less than Abs(b).
-  if (AA.CompareToAbsoluteValues(AB) >= 0) then
+  compare := AA.CompareToAbsoluteValues(AB);
+  if compare = 0 then
+  begin
+    Result := Zero;
+    Exit;
+  end;
+
+  if compare > 0 then
   begin
     a := AA;
     b := AB;

From 9c951073d9ed5e8b4c683e883184b93f9ab878f9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20M=C3=BCller?= <stefan.mueller@aksdb.de>
Date: Mon, 20 May 2024 00:56:52 +0200
Subject: [PATCH 2/3] Removed irrelevant todo

---
 UBigInt.pas | 1 -
 1 file changed, 1 deletion(-)

diff --git a/UBigInt.pas b/UBigInt.pas
index 4c8505e..7d22c07 100644
--- a/UBigInt.pas
+++ b/UBigInt.pas
@@ -572,7 +572,6 @@ begin
     Result := TBigInt.MultiplyAbsoluteValues(A, B, A.IsNegative <> B.IsNegative);
 end;
 
-// TODO: Shift operator could be implemented with a single Move call, but I do not want to change it without test cases.
 operator shl(const A: TBigInt; const B: Integer): TBigInt;
 var
   i, j, digitShifts, bitShifts, reverseShift, len, newLength: Integer;

From 2ca960f19c69e64e4cf5751476655df7d69b494f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20M=C3=BCller?= <stefan.mueller@aksdb.de>
Date: Mon, 20 May 2024 00:59:40 +0200
Subject: [PATCH 3/3] Added TBigInt.ToString for debugging

---
 UBigInt.pas | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/UBigInt.pas b/UBigInt.pas
index 7d22c07..5a31b72 100644
--- a/UBigInt.pas
+++ b/UBigInt.pas
@@ -78,6 +78,8 @@ type
     class property Zero: TBigInt read GetZero;
     function CompareTo(constref AOther: TBigInt): Integer;
     function TryToInt64(out AOutput: Int64): Boolean;
+    // TODO: ToString is currently for debug output only.
+    function ToString: string;
     class function FromInt64(const AValue: Int64): TBigInt; static;
     class function FromHexadecimalString(const AValue: string): TBigInt; static;
     class function FromBinaryString(const AValue: string): TBigInt; static;
@@ -498,6 +500,21 @@ begin
   end;
 end;
 
+function TBigInt.ToString: string;
+var
+  i: Integer;
+begin
+  if FIsNegative then
+    Result := '-'
+  else
+    Result := '';
+  for i := 0 to Length(FDigits) - 2 do
+    Result := Result + '(' + IntToStr(FDigits[i]) + ' + 2^32 * ';
+  Result := Result + IntToStr(FDigits[Length(FDigits) - 1]);
+  for i := 0 to Length(FDigits) - 2 do
+    Result := Result + ')';
+end;
+
 class function TBigInt.FromInt64(const AValue: Int64): TBigInt;
 var
   absVal: Int64;