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added: to Big::Add Big::Sub Big::Mul Big::Div 

second parameter 'bool round = true'
         the rounding is made if it is true
changed: in Big::ToString_CreateNewMantissaAndExponent()
         we should use dividing without rounding
         consider this 32 bit binary value:
         1.1111111111111111111111111111111
         previous the result from converting (to the base 10) was equal 2
         now is 1.999999
      



git-svn-id: svn://ttmath.org/publicrep/ttmath/trunk@263 e52654a7-88a9-db11-a3e9-0013d4bc506e
This commit is contained in:
Tomasz Sowa 2009-12-14 12:16:32 +00:00
parent 82711f4441
commit 418db51f46
1 changed files with 17 additions and 25 deletions
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42
ttmath/ttmathbig.h
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@ -869,7 +869,7 @@ public:
it returns carry if the sum is too big
*/
uint Add(Big<exp, man> ss2)
uint Add(Big<exp, man> ss2, bool round = true)
{
Int<exp> exp_offset( exponent );
@ -904,7 +904,7 @@ public:
if( do_adding )
c += AddMantissas(ss2, last_bit_set, rest_zero, do_rounding, rounding_up);
if( do_rounding && last_bit_set )
if( round && do_rounding && last_bit_set )
c += RoundHalfToEven(rest_zero, rounding_up);
if( do_adding || (do_rounding && last_bit_set) )
@ -919,11 +919,11 @@ public:
it returns carry if the result is too big
*/
uint Sub(Big<exp, man> ss2)
uint Sub(Big<exp, man> ss2, bool round = true)
{
ss2.ChangeSign();
return Add(ss2);
return Add(ss2, round);
}
@ -1233,7 +1233,7 @@ public:
multiplication this = this * ss2
this method returns a carry
*/
uint Mul(const Big<exp, man> & ss2)
uint Mul(const Big<exp, man> & ss2, bool round = true)
{
TTMATH_REFERENCE_ASSERT( ss2 )
@ -1272,7 +1272,7 @@ public:
for(i=0 ; i<man ; ++i)
mantissa.table[i] = man_result.table[i+man];
if( (man_result.table[man-1] & TTMATH_UINT_HIGHEST_BIT) != 0 )
if( round && (man_result.table[man-1] & TTMATH_UINT_HIGHEST_BIT) != 0 )
{
bool is_half = CheckGreaterOrEqualHalf(man_result.table, man);
c += RoundHalfToEven(is_half);
@ -1304,7 +1304,7 @@ public:
1 - carry (in a division carry can be as well)
2 - improper argument (ss2 is zero)
*/
uint Div(const Big<exp, man> & ss2)
uint Div(const Big<exp, man> & ss2, bool round = true)
{
TTMATH_REFERENCE_ASSERT( ss2 )
@ -1348,10 +1348,10 @@ public:
for(i=0 ; i<man ; ++i)
mantissa.table[i] = man1.table[i+man];
if( (man1.table[man-1] & TTMATH_UINT_HIGHEST_BIT) != 0 )
if( round && (man1.table[man-1] & TTMATH_UINT_HIGHEST_BIT) != 0 )
{
bool is_half = CheckGreaterOrEqualHalf(man1.table, man);
c += RoundHalfToEven(is_half);
c += RoundHalfToEven(is_half, true);
}
if( IsSign() == ss2.IsSign() )
@ -3225,24 +3225,12 @@ private:
*/
Int<exp+1> new_exp;
if( ToString_CreateNewMantissaAndExponent(result, conv, new_exp) )
if( ToString_CreateNewMantissaAndExponent<string_type, char_type>(result, conv, new_exp) )
{
Misc::AssignString(result, error_overflow_msg);
return 1;
}
/*
we're rounding the mantissa only if the base is different from 2,4,8 or 16
(this formula means that the number of bits in the base is greater than one)
*/
if( conv.base_round && conv.base!=2 && conv.base!=4 && conv.base!=8 && conv.base!=16 )
{
if( ToString_BaseRound<string_type, char_type>(result, conv, new_exp) )
{
Misc::AssignString(result, error_overflow_msg);
return 1;
}
}
if( ToString_SetCommaAndExponent<string_type, char_type>(result, conv, new_exp) )
{
@ -3313,7 +3301,7 @@ private:
M = mm * 2^ee where ee will be <= 0
next we'll move all bits of mm into the right when ee is equal zero
abs(ee) must not to be too big that only few bits from mm we can leave
abs(ee) must not be too big that only few bits from mm we can leave
then we'll have:
M = mmm * 2^0
@ -3327,7 +3315,7 @@ private:
but we need 'new'exp' as integer then we take:
new_exp = [log base (2^exponent)] + 1 <- where [x] means integer value from x
*/
template<class string_type>
template<class string_type, class char_type>
uint ToString_CreateNewMantissaAndExponent( string_type & new_man, const Conv & conv,
Int<exp+1> & new_exp) const
{
@ -3389,7 +3377,7 @@ private:
// the sign don't interest us here
temp.mantissa = mantissa;
temp.exponent = exponent;
c += temp.Div( base_ );
c += temp.Div(base_, false); // dividing without rounding
// moving all bits of the mantissa into the right
// (how many times to move depend on the exponent)
@ -3406,6 +3394,10 @@ private:
// shouldn't have had a carry
// (in the future this can be changed)
// base rounding
if( conv.base_round )
c += ToString_BaseRound<string_type, char_type>(new_man, conv, new_exp);
return (c==0)? 0 : 1;
}