Is there a C++ equivalent to Java's BigDecimal?

Question

I\'m looking for a C++ class that can do decimal floating point arithmetic. Looking through http://speleotrove.com/decimal/ there are links to all sorts of classes that peop

Answer 1

Here is an implementation of BCMath PHP to C++. There are two versions, one for Qt and the other for use only STL.

Source: https://github.com/DesarrollosCuado/BCMath-for-Cpp

BCMath::bcscale(4); //Num Decimals
BCMath test("-5978");

test^=30; //Pow, only integers. Not work decimals.
std::cout<<"Result BigDecimal 1: "<<test.toString().c_str()<<std::endl;

test-=1.23; //sub
std::cout<<"Result BigDecimal 2: "<<test.toString().c_str()<<std::endl;

test*=1.23; //mul
std::cout<<"Result BigDecimal 3: "<<test.toString().c_str()<<std::endl;

test*=-1.23; //mul
std::cout<<"Result BigDecimal 4: "<<test.toString().c_str()<<std::endl;

BCMath::bcscale(70); //Num Decimals

BCMath randNum("-5943534512345234545.8998928392839247844353457");
BCMath pi("3.1415926535897932384626433832795028841971693993751058209749445923078164062862");

BCMath result1 = randNum + pi;
BCMath result2 = randNum - pi;
BCMath result3 = randNum * pi;
BCMath result4 = randNum / pi;

std::cout<<"Result Super Precision 1: "<<result1.toString().c_str()<<std::endl;
std::cout<<"Result Super Precision 2: "<<result2.toString().c_str()<<std::endl;
std::cout<<"Result Super Precision 3: "<<result3.toString().c_str()<<std::endl;
std::cout<<"Result Super Precision 4: "<<result4.toString().c_str()<<std::endl;

//Other example
BCMath::bcscale(4); //Num Decimals
std::cout<<"Other 1: "<<BCMath::bcmul("1000000.0134", "8.0234").c_str()<<std::endl;
std::cout<<"Other 2: "<<BCMath::bcadd("1000000.0134", "8.0234").c_str()<<std::endl;

std::cout<<"Compare 1:  "<<BCMath::bccomp("1", "2")<<std::endl;
std::cout<<"Compare 2:  "<<BCMath::bccomp("1.00001", "1", 3)<<std::endl;
std::cout<<"Compare 3:  "<<BCMath::bccomp("1.00001", "1", 5)<<std::endl;
std::cout<<"Compare 4:  "<<(BCMath("1")< BCMath("2"))<<std::endl;
std::cout<<"Compare 5:  "<<(BCMath("1")<=BCMath("2"))<<std::endl;
std::cout<<"Compare 6:  "<<(BCMath("1")> BCMath("2"))<<std::endl;
std::cout<<"Compare 7:  "<<(BCMath("1")>=BCMath("2"))<<std::endl;
std::cout<<"Compare 8:  "<<(BCMath("2")< BCMath("2"))<<std::endl;
std::cout<<"Compare 9:  "<<(BCMath("2")<=BCMath("2"))<<std::endl;
std::cout<<"Compare 10: "<<(BCMath("2")> BCMath("2"))<<std::endl;
std::cout<<"Compare 11: "<<(BCMath("2")>=BCMath("2"))<<std::endl;

std::cout<<"Round 1: "<<BCMath::bcround("123.01254").c_str()<<std::endl;
std::cout<<"Round 2: "<<BCMath::bcround("-123.01254", 3).c_str()<<std::endl;
std::cout<<"Round 3: "<<BCMath::bcround("123.01254", 2).c_str()<<std::endl;
pi.round(3);
std::cout<<"Round 4: "<<pi.toString().c_str()<<std::endl;

BCMath part1("-.123");
BCMath part2(".123");
BCMath part3("123");
std::cout<<"Int part 1: "<<part1.getIntPart().c_str()<<std::endl;
std::cout<<"Dec part 1: "<<part1.getDecPart().c_str()<<std::endl;
std::cout<<"Int part 2: "<<part2.getIntPart().c_str()<<std::endl;
std::cout<<"Dec part 2: "<<part2.getDecPart().c_str()<<std::endl;
std::cout<<"Int part 3: "<<part3.getIntPart().c_str()<<std::endl;
std::cout<<"Dec part 3: "<<part3.getDecPart().c_str()<<std::endl;

Result:

Result BigDecimal 1:  198005530669253749533290222782634796336450786581284861381777714804795900171726938603997395193921984842256586113024
Result BigDecimal 2:  198005530669253749533290222782634796336450786581284861381777714804795900171726938603997395193921984842256586113022.7700
Result BigDecimal 3:  243546802723182111925946974022640799493834467494980379499586589209898957211224134482916796088524041355975600919018.0071
Result BigDecimal 4:  -299562567349513997668914778047848183377416395018825866784491504728175717369805685413987659188884570867849989130392.1487

Result Super Precision 1:  -5943534512345234542.7583001856941315459727023167204971158028306006248941790250554076921835
Result Super Precision 2:  -5943534512345234549.0414854928737180228979890832795028841971693993751058209749445923078164
Result Super Precision 3:  -18672164360341183116.9114783895073349180904753962992796943871920962352436079118338887287186
Result Super Precision 4:  -1891885794154043400.2804849527556211973567525043250278948318788149660700494315139982452600

Other 1:  8023400.1075
Other 2:  1000008.0368

Compare 1:   -1
Compare 2:   0
Compare 3:   1
Compare 4:   true
Compare 5:   true
Compare 6:   false
Compare 7:   false
Compare 8:   false
Compare 9:   true
Compare 10:  false
Compare 11:  true

Round 1:  123.0125
Round 2:  -123.013
Round 3:  123.01
Round 4:  3.142

Int part 1:  -0
Dec part 1:  123
Int part 2:  0
Dec part 2:  123
Int part 3:  123
Dec part 3:  0

Answer 2

If you need to do operations with HUGE decimal values I would suggest you to use http://gmplib.org/ library. I've used it a lot with C and C++.