What data type should be used as a key for a monetary equivalent?

For monetary equivalents, a data type that can accurately represent fixed-point decimal numbers should be used to avoid rounding errors inherent in floating-point types (float, double).

The most suitable options are:

• long long (in combination with scaling): Store the monetary value as an integer in the smallest units (e.g., kopecks, cents). This ensures accuracy and avoids floating-point issues.

  long long amount_in_kopecks = 12345; // 123 rubles 45 kopecks
  

• Library for working with decimal numbers: Use specialized libraries that provide data types for financial calculations. This is the preferred option for complex operations and maximum accuracy. Examples: GMP, Boost.Multiprecision.

  // Example using a hypothetical Decimal library
  Decimal amount = "123.45";
  

Should not be used:

• float, double: Can lead to rounding errors in precise financial calculations.