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FAQ.md

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Frequently Asked Questions

Why not use decimal C# data data type ?

Decimal in C# is just not that good.

  • It is uses 12 bytes for mantissa (effectively 16)
  • It does not have CLR support. i.e. all operators will be working as functions (slower than DFP).TODO: Benchmark proof.

What is the Decimal64Utils.NULL?

Is Java all the custom data types can be represented only by the classes. This is very expensive. This requires much amount of memory and make a big pressure on the garbage collector. But you can avoid this. You can work with decimal values packed to the long primitives. So, the replacing the Decimal64 class with the long values looks as a great idea till you encounter null reference. How to represent null with the long? Decimal64 solves this problem by introducing special Decimal64Utils.NULL value. According to the IEEE 754-2008, the NaN value can be encoded in different ways. Just one value from the whole NaN combinations was used as Decimal64Utils.NULL. But, since this value is NaN according to the standard, the Decimal64Utils.isNaN(Decimal64Utils.NULL) returns true. You should also keep this in mind if you plan to use the ValueTypeAgent. So, key points:

  • There is no NULL value in IEEE 754-2008 standard.
  • The NULL is just a one combination of possible NaN values.
  • Decimal64Utils.isNaN(Decimal64Utils.NULL) returns true.

What are the *Checked functions in Java?

The *Checked functions in Java are not intended to be used directly. These special functions are required just for ValueTypeAgent support.

How to quickly check a sign?

There are many is* functions in the DFP library for the fast sign check. The output values of these functions are presented in the next table.

Function -Infinity -1 0 1 Infinity NaN
isPositive false false false TRUE TRUE false
isNonNegative false false TRUE TRUE TRUE false
isNegative TRUE TRUE false false false false
isNonPositive TRUE TRUE TRUE false false false
isInfinity TRUE false false false TRUE false
isPositiveInfinity false false false false TRUE false
isNegativeInfinity TRUE false false false false false
isNaN false false false false false TRUE
isFinite false TRUE TRUE TRUE false false
isNonFinite TRUE false false false TRUE TRUE
isZero false false TRUE false false false
isNonZero TRUE TRUE false TRUE TRUE TRUE

Do we have a method of parsing value like "1.703E-5"?

All the parse() and tryParse() methods supports this scientific notation. Use the method you like best

Decimal64Utils.parse() or Decimal64Utils.tryParse()
Decimal64.parse() or Decimal64.tryParse()