Decimal data type for C++
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Decimal data type support, for COBOL-like fixed-point operations on currency/money values.

Author: Piotr Likus

Created: 03/01/2011

Modified: 18/02/2017

Licence: BSD

Version: 1.15

This data type is designed to perform calculation with on-fly roundings & to support correct compare function (floating-point compare is unreliable).

Values are stored internally using 64-bit integer, so maximum number of digits is 18.

Precision is user-defined, so you can use this data type for currency rates.

To store decimal in file you can use "unbiased" functions or use stream i/o.


Example usage:

#include "decimal.h"

using namespace dec;
using namespace std;

// the following declares currency variable with 2 decimal points
// initialized with integer value (can be also floating-point)
decimal<2> value(143125);

// displays: Value #1 is: 143125.00
cout << "Value #1 is: " << value << endl;

// declare precise value with digits after decimal point
decimal<2> b("0.11");

// perform calculations as with any other numeric type
value += b;

// displays: Value #2 is: 143125.11
cout << "Value #2 is: " << value << endl;

// automatic rounding performed here
value /= 1000;

// displays: Value #3 is: 143.13
cout << "Value #3 is: " << value << endl;

// integer multiplication and division can be used directly in expression
// displays: Value: 143.13 * 2 is: 286.26
cout << "Value: " << value << " * 2 is: " << (value * 2) << endl;

// to use non-integer constants in expressions you need to use decimal_cast
value = value * decimal_cast<2>("3.33") / decimal_cast<2>(333.0);

// displays: Value #4 is: 1.43
cout << "Value #4 is: " << value << endl;

// to mix decimals with different precision use decimal_cast
// it will round result automatically
decimal<6> exchangeRate(12.1234);
value = decimal_cast<2>(decimal_cast<6>(value) * exchangeRate);

// displays: Value #5 is: 17.34
cout << "Value #5 is: " << value << endl;

Supported rounding modes:

  • def_round_policy: default rounding (arithmetic)
  • null_round_policy: round towards zero = truncate
  • half_down_round_policy: round half towards negative infinity
  • half_up_round_policy: round half towards positive infinity
  • half_even_round_policy: bankers' rounding, convergent rounding, statistician's rounding, Dutch rounding, Gaussian rounding
  • ceiling_round_policy: round towards positive infinity
  • floor_round_policy: round towards negative infinity
  • round_down_round_policy: round towards zero = truncate
  • round_up_round_policy: round away from zero

In order to use one of these rounding modes you need to declare your decimal variable like this:

dec::decimal<2, half_even_round_policy> a;

and it will perform required rounding automatically - for example during assignment or arithmetic operations.

Other information

For more examples please see \test directory.

Directory structure:

\doc     - documentation (licence etc.)
\include - headers
\test    - unit tests, Boost-based

Code documentation can be generated using Doxygen:

Tested compilers:

  • VS2015 Community
  • VS2013 Community Update 4
  • Code::Blocks 13.12 + MinGW + gcc 4.8.4

Uses C++11 by default, define DEC_NO_CPP11 symbol if your compiler does not support this standard. To use custom namespace, define DEC_NAMESPACE symbol which should contain your target namespace for decimal type.

For list of project contributors, currently open issues or latest version see project site: