Package dev.frostlake.values

Class ApproximateValues

java.lang.Object
dev.frostlake.values.ApproximateValues
public final class ApproximateValues extends Object
The APPROXIMATE family's runtime carrier is a Java double, and these are the rules that follow from it.

★ A FLOAT COLUMN HOLDS A DOUBLE. Live-verified on every write path — INSERT … VALUES, INSERT … SELECT, UPDATE, MERGE, CTAS, a column DEFAULT, a text value, an integer — a value written into a FLOAT column becomes the nearest double: a stored 0.1 reads back as 0.10000000000000000555 through ::NUMBER(38,20), a stored nineteen-digit integer becomes 1234567890123456768, and a stored -0.0::FLOAT keeps its sign. Frostlake used to keep whatever class the value arrived in, so the same column held a BigDecimal, a Long or a Double depending on how the row was written, and every one of those cells disagreed with the account.

★ A FLOAT BESIDE AN EXACT NUMBER COMPARES AS A DOUBLE. Live answers TRUE for 1234567890123456789::FLOAT = 1234567890123456768 and for 0.1::FLOAT = 0.10000000000000000555: the exact side is converted to a double and the two doubles are compared. Comparing through the double's shortest decimal spelling, as this engine did, made both FALSE.

★ NEGATIVE ZERO IS A VALUE OF ITS OWN, and equal to zero. -0.0::FLOAT = 0.0::FLOAT is TRUE and -0.0::FLOAT < 0 is FALSE, while a tie between the two keeps whichever was seen FIRST — GREATEST, LEAST, MIN and MAX all answer -0 when it leads. ORDER BY is the one place with a tie-break: -0 sorts before 0.

  • Method Summary

    Modifier and Type
    Method
    Description
    static int
    compare(double left, double right)
    Two doubles compared as VALUES: -0.0 and 0.0 are equal, so a tie keeps the first seen.
    static boolean
    isApproximate(Object value)
    Whether a runtime value is carried as a double.
    static int
    order(double left, double right)
    Two doubles compared for SORTING, which is the one place the two zeros are told apart: -0 sorts before 0, as it does on the account.
    static Double
    written(Object value)
    The double a value takes when written into an approximate column, or null when the value is not numeric text or a number at all (a boolean, a variant) and the caller keeps it as it is.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Method Details

    • written

      public static Double written(Object value)
      The double a value takes when written into an approximate column, or null when the value is not numeric text or a number at all (a boolean, a variant) and the caller keeps it as it is.
      Parameters:
      value - the value as the write produced it
      Returns:
      its double, or null

    • isApproximate

      public static boolean isApproximate(Object value)
      Whether a runtime value is carried as a double.
      Parameters:
      value - any value
      Returns:
      true for a Double or a Float

    • compare

      public static int compare(double left, double right)
      Two doubles compared as VALUES: -0.0 and 0.0 are equal, so a tie keeps the first seen. NaN keeps its place in the total order — it equals itself and outranks everything.
      Parameters:
      left - one value
      right - the other
      Returns:
      negative, zero or positive

    • order

      public static int order(double left, double right)
      Two doubles compared for SORTING, which is the one place the two zeros are told apart: -0 sorts before 0, as it does on the account.
      Parameters:
      left - one value
      right - the other
      Returns:
      negative, zero or positive