decimal

A signed decimal floating point number. Either a decimal point (.) or an exponent symbol (e) must be present within the number for it to be a valid decimal, plus a decimal suffix (d) to distinguish it from a float.

When perfect accuracy of base-10 numbers is a requirement, use the decimal type in place of the float type. When extremely small floating point variations are acceptable, you might choose to use the float type to obtain better performance.

Values of the decimal type are a finite-precision approximation of the mathematical real numbers, encoded as 64-bit decimal floating-point values consisting of sign, significand, and exponent, as defined by the IEEE Standard for Floating-Point Arithmetic, ANSI/IEEE Standard 754 -2008 (IEEE, New York). Values of the decimal type have a precision of exactly 16 decimal digits.

The largest positive decimal floating point value that can be stored in a variable of type decimal is 9.999999999999999 * 10384 and the smallest nonzero positive value that can be stored is 10-398.

In addition to the usual positive and negative numbers, the IEEE standard also defines positive and negative zeros, positive and negative infinities, and Not-a-Number values. For information about how the correlator handles these values, see Support for IEEE 754 special values.

Because decimal values are of finite precision, they cannot accurately represent all values, for example, recurring decimals or irrational numbers. However, decimals have the advantage over floats in that provided a decimal literal does not exceed the 16-place precision, it will be represented exactly within the correlator. The following program illustrates the difference between decimal and float types in this regard:

monitor foo
{
   action onload()
   {
      float f;
      decimal d;
      f := 0.1;
      d := 0.1d;
      print f.formatFixed(18);
      print d.formatFixed(18);
   }
}

This program produces the output below. Note the small error in the least significant digit in the float, versus the decimal.

There are a number of decimal constants provided in EPL. See Support for IEEE 754 special values.

The EPL operators that you can use with decimal types are the same operators that you can use with float types. For information on these operators, see float.

The methods that you can call on decimal types are the same methods that you can call on float types. For information on these methods, see float. There are a few differences according to whether the method is called on a decimal or float type and these are noted in the descriptions.