diff --git a/CHANGELOG b/CHANGELOG
index 6e872be..c79b4a6 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,41 @@
+Version 0.8.1 (2007.04.17):
+	* fixed: Big::PowFrac(..) didn't return a correct error code
+	  (when 'this' was negative)
+	* added: Root(x; index) (and to the parser as well)
+	* added: macro: TTMATH_PRERELEASE_VER (can be either zero or one)
+	* added: UInt::MulInt(int, UInt<int another_size>::&)
+	* added: Big::MulUInt(uint)
+	* changed: Big::MulInt(sint)
+	* added: Big::ToUInt(uint &)
+	* changed: Big::ToInt(sint&)
+	* changed: Factorial() it uses Big::MulUInt() at the beginning
+	  (faster now especially more on a 32bit platform)
+	* added: doxygen.cfg for generating a documentation from the doxygen
+	* changed: UInt::Rcl(uint c=0) and UInt::Rcr(uint c=0) into
+	  UInt::Rcl2(uint bits, uint c) and UInt::Rcr2(uint bits, uint c)
+	  now they can move more than one bit and they are only private
+	* fixed: UInt::Rcl(uint bits, uint c) and UInt::Rcr(uint bits, uint c)
+	  didn't correctly return a carry if the 'bits' were equal
+	  to 'value_size*TTMATH_BITS_PER_UINT'
+	* changed: UInt::Rcl(uint bits, uint c) and UInt::Rcr(uint bits, uint c)
+	  into UInt::Rcl(uint bits, uint c=0) and
+	  UInt::Rcr(uint bits, uint c=0)
+	  they are faster now when the bits is greater than a half of
+	  the TTMATH_BITS_PER_UINT
+	* changed: UInt::CompensationToLeft() it's faster now
+	* changed: more small changes where there were UInt::Rcl(uint c=0) and
+	  UInt::Rcr(uint c=0) used
+	* changed: as the Big type uses UInt::Rcl() and UInt::Rcr() a lot then
+	  it is much faster now (about 5-25%)
+	* added: ASinh(), ACosh(), ATanh() /ATgh()/, ACoth() /ACtgh()/
+	  and to the parser as well
+	* added: UInt::BitAnd(), UInt::BitOr(), UInt::BitXor(), UInt::BitNot(),
+	  Big::BitAnd(), Big::BitOr(), Big::BitXor()
+	* added: to the parser: bitand(), bitor(), bitxor()
+	  /band(), bor(), bxor()/
+	* changed: the way of parsing operators in the mathematical parser
+	  (the parser is not too much greedy now)
+	
 Version 0.8.0 (2007.03.28):
 	* added: into the parser: SetFactorialMax()
 	* added: DegToDeg(deg, min, sec), DegToRad(deg), DegToRad(deg, min, sec),
diff --git a/ttmath/ttmathbig.h b/ttmath/ttmathbig.h
index 7a6c47c..26f741b 100644
--- a/ttmath/ttmathbig.h
+++ b/ttmath/ttmathbig.h
@@ -549,7 +549,7 @@ public:
 		exp_offset.Sub( ss2.exponent );
 		exp_offset.Abs();
 
-		// abs(this) will be >= abs(ss2)
+		// (1) abs(this) will be >= abs(ss2)
 		if( SmallerWithoutSignThan(ss2) )
 		{
 			Big<exp, man> temp(ss2);
@@ -567,11 +567,12 @@ public:
 		else
 		if( exp_offset < mantissa_size_in_bits )
 		{
-			// moving 'exp_offset' times
+			// (2) moving 'exp_offset' times
 			ss2.mantissa.Rcr( exp_offset.ToInt(), 0 );
 		}
 		else
 		{
+			// (3) 
 			// exp_offset == mantissa_size_in_bits
 			// we're rounding 'this' about one (up or down depending on a ss2 sign)
 			ss2.mantissa.SetOne();
@@ -590,11 +591,12 @@ public:
 		else
 		{
 			// values have different signs
-			if( mantissa.Sub(ss2.mantissa) )
-			{
-				mantissa.Rcl(1,1);  // maybe without this rcl and subone()? !!!!
-				c = exponent.SubOne();
-			}
+			// there shouldn't be a carry here because
+			// (1) (2) and (3) guarantee that the mantissa of this
+			// is greater than the mantissa of the ss2
+			uint c_temp = mantissa.Sub(ss2.mantissa);
+
+			TTMATH_ASSERT( c_temp == 0 )
 		}
 
 		c += Standardizing();
diff --git a/ttmath/ttmathparser.h b/ttmath/ttmathparser.h
index 2a8f008..b72359a 100644
--- a/ttmath/ttmathparser.h
+++ b/ttmath/ttmathparser.h
@@ -1619,13 +1619,22 @@ void CreateMathematicalOperatorsTable()
 }
 
 
-bool CanBeMathematicalOperator(unsigned char c)
-{
-	if( c=='|' || c=='&' || c=='!' || c=='=' || c=='<' || c=='>' ||
-		c=='*' || c=='/' || c=='+' || c=='-' || c=='^' )
-	return true;
+/*!
+	returns true if 'str2' is the substring of str1
 
-return false;
+	e.g.
+	true when str1="test" and str2="te"
+*/
+bool IsSubstring(const std::string & str1, const std::string & str2)
+{
+	if( str2.length() > str1.length() )
+		return false;
+
+	for(std::string::size_type i=0 ; i<str2.length() ; ++i)
+		if( str1[i] != str2[i] )
+			return false;
+
+return true;
 }
 
 
@@ -1635,17 +1644,31 @@ return false;
 void ReadMathematicalOperator(Item & result)
 {
 std::string oper;
+typename OperatorsTable::iterator iter_old, iter_new;
 
-	for( ; CanBeMathematicalOperator(*pstring) ; ++pstring )
+	iter_old = operators_table.end();
+
+	for( ; true ; ++pstring )
+	{
 		oper += *pstring;
+		iter_new = operators_table.lower_bound(oper);
+		
+		if( iter_new == operators_table.end() || !IsSubstring(iter_new->first, oper) )
+		{
+			oper.erase( --oper.end() ); // we've got mininum one element
 
-	typename OperatorsTable::iterator iter = operators_table.find(oper);
-
-	if( iter == operators_table.end() )
-		Error( err_unknown_operator );
-
-	result.type = Item::mat_operator;
-	result.moperator.SetType( iter->second );
+			if( iter_old != operators_table.end() && iter_old->first == oper )
+			{
+				result.type = Item::mat_operator;
+				result.moperator.SetType( iter_old->second );
+				break;
+			}
+			
+			Error( err_unknown_operator );
+		}
+	
+		iter_old = iter_new;
+	}
 }
 
 
@@ -1676,10 +1699,7 @@ int ReadOperator(Item & result)
 		++pstring;
 	}
 	else
-	if( CanBeMathematicalOperator(*pstring) )
 		ReadMathematicalOperator(result);
-	else
-		Error( err_unknown_character );
 
 return 0;
 }
diff --git a/ttmath/ttmathtypes.h b/ttmath/ttmathtypes.h
index 2a38b7d..414170b 100644
--- a/ttmath/ttmathtypes.h
+++ b/ttmath/ttmathtypes.h
@@ -65,7 +65,7 @@
 #define TTMATH_MAJOR_VER		0
 #define TTMATH_MINOR_VER		8
 #define TTMATH_REVISION_VER		1
-#define TTMATH_PRERELEASE_VER	1
+#define TTMATH_PRERELEASE_VER	0
 
 
 /*!