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## org.apache.commons.math.dfp
Class Dfp

    java.lang.Object
      org.apache.commons.math.dfp.Dfp

All Implemented Interfaces:
  FieldElement<Dfp>

Direct Known Subclasses:
  DfpDec

    public class Dfp

extends Object
implements FieldElement<Dfp>

Decimal floating point library for Java

Another floating point class. This one is built using radix 10000 which is 104, so its almost decimal.

The design goals here are:

1. Decimal math, or close to it
2. Settable precision (but no mix between numbers using different settings)
3. Portability. Code should be keep as portable as possible.
4. Performance
5. Accuracy - Results should always be +/- 1 ULP for basic algebraic operation
6. Comply with IEEE 854-1987 as much as possible. (See IEEE 854-1987 notes below)

Trade offs:

1. Memory foot print. I'm using more memory than necessary to represent numbers to get better performance.
2. Digits are bigger, so rounding is a greater loss. So, if you really need 12 decimal digits, better use 4 base 10000 digits there can be one partially filled.

Numbers are represented in the following form:

      n  =  sign × mant × (radix)exp;

where sign is ±1, mantissa represents a fractional number between zero and one. mant[0] is the least significant digit. exp is in the range of -32767 to 32768

IEEE 854-1987 Notes and differences

IEEE 854 requires the radix to be either 2 or 10. The radix here is 10000, so that requirement is not met, but it is possible that a subclassed can be made to make it behave as a radix 10 number. It is my opinion that if it looks and behaves as a radix 10 number then it is one and that requirement would be met.

The radix of 10000 was chosen because it should be faster to operate on 4 decimal digits at once instead of one at a time. Radix 10 behavior can be realized by add an additional rounding step to ensure that the number of decimal digits represented is constant.

The IEEE standard specifically leaves out internal data encoding, so it is reasonable to conclude that such a subclass of this radix 10000 system is merely an encoding of a radix 10 system.

IEEE 854 also specifies the existence of "sub-normal" numbers. This class does not contain any such entities. The most significant radix 10000 digit is always non-zero. Instead, we support "gradual underflow" by raising the underflow flag for numbers less with exponent less than expMin, but don't flush to zero until the exponent reaches MIN_EXP-digits. Thus the smallest number we can represent would be: 1E(-(MIN_EXP-digits-1)*4), eg, for digits=5, MIN_EXP=-32767, that would be 1e-131092.

IEEE 854 defines that the implied radix point lies just to the right of the most significant digit and to the left of the remaining digits. This implementation puts the implied radix point to the left of all digits including the most significant one. The most significant digit here is the one just to the right of the radix point. This is a fine detail and is really only a matter of definition. Any side effects of this can be rendered invisible by a subclass.

Since:
  2.2
Version:
  $Revision: 1003889 $ $Date: 2010-10-02 23:11:55 +0200 (sam. 02 oct. 2010) $
See Also:
  `DfpField`

Field Summary
`static int` | `ERR_SCALE` The amount under/overflows are scaled by before going to trap handler
`protected int` | `exp` Exponent.
`static byte` | `FINITE` Indicator value for normal finite numbers.
`static byte` | `INFINITE` Indicator value for Infinity.
`protected int[]` | `mant` Mantissa.
`static int` | `MAX_EXP` The maximum exponent before overflow is signaled and results flushed to infinity
`static int` | `MIN_EXP` The minimum exponent before underflow is signaled.
`protected byte` | `nans` Indicator for non-finite / non-number values.
`static byte` | `QNAN` Indicator value for quiet NaN.
`static int` | `RADIX` The radix, or base of this system.
`protected byte` | `sign` Sign bit: & for positive, -1 for negative.
`static byte` | `SNAN` Indicator value for signaling NaN.

Constructor Summary
`` | `Dfp(Dfp d)` Copy constructor.
`protected` | `Dfp(DfpField field)` Makes an instance with a value of zero.
`protected` | `Dfp(DfpField field, byte x)` Create an instance from a byte value.
`protected` | `Dfp(DfpField field, byte sign, byte nans)` Creates an instance with a non-finite value.
`protected` | `Dfp(DfpField field, double x)` Create an instance from a double value.
`protected` | `Dfp(DfpField field, int x)` Create an instance from an int value.
`protected` | `Dfp(DfpField field, long x)` Create an instance from a long value.
`protected` | `Dfp(DfpField field, String s)` Create an instance from a String representation.

Method Summary
`Dfp` | `add(Dfp x)` Add x to this.
`protected int` | `align(int e)` Make our exp equal to the supplied one, this may cause rounding.
`Dfp` | `ceil()` Round to an integer using the round ceil mode.
`int` | `classify()` Returns the type - one of FINITE, INFINITE, SNAN, QNAN.
`protected int` | `complement(int extra)` Negate the mantissa of this by computing the complement.
`static Dfp` | `copysign(Dfp x, Dfp y)` Creates an instance that is the same as x except that it has the sign of y.
`protected String` | `dfp2sci()` Convert an instance to a string using scientific notation.
`protected String` | `dfp2string()` Convert an instance to a string using normal notation.
`Dfp` | `divide(Dfp divisor)` Divide this by divisor.
`Dfp` | `divide(int divisor)` Divide by a single digit less than radix.
`Dfp` | `dotrap(int type, String what, Dfp oper, Dfp result)` Raises a trap.
`boolean` | `equals(Object other)` Check if instance is equal to x.
`Dfp` | `floor()` Round to an integer using the round floor mode.
`DfpField` | `getField()` Get the `Field` (really a `DfpField`) to which the instance belongs.
`Dfp` | `getOne()` Get the constant 1.
`int` | `getRadixDigits()` Get the number of radix digits of the instance.
`Dfp` | `getTwo()` Get the constant 2.
`Dfp` | `getZero()` Get the constant 0.
`boolean` | `greaterThan(Dfp x)` Check if instance is greater than x.
`int` | `hashCode()` Gets a hashCode for the instance.
`int` | `intValue()` Convert this to an integer.
`boolean` | `isInfinite()` Check if instance is infinite.
`boolean` | `isNaN()` Check if instance is not a number.
`boolean` | `lessThan(Dfp x)` Check if instance is less than x.
`int` | `log10()` Get the exponent of the greatest power of 10 that is less than or equal to abs(this).
`int` | `log10K()` Get the exponent of the greatest power of 10000 that is less than or equal to the absolute value of this.
`Dfp` | `multiply(Dfp x)` Multiply this by x.
`Dfp` | `multiply(int x)` Multiply this by a single digit 0<=x<radix.
`Dfp` | `negate()` Returns a number that is this number with the sign bit reversed.
`Dfp` | `newInstance()` Create an instance with a value of 0.
`Dfp` | `newInstance(byte x)` Create an instance from a byte value.
`Dfp` | `newInstance(byte sig, byte code)` Creates an instance with a non-finite value.
`Dfp` | `newInstance(Dfp d)` Create an instance by copying an existing one.
`Dfp` | `newInstance(double x)` Create an instance from a double value.
`Dfp` | `newInstance(int x)` Create an instance from an int value.
`Dfp` | `newInstance(long x)` Create an instance from a long value.
`Dfp` | `newInstance(String s)` Create an instance from a String representation.
`Dfp` | `nextAfter(Dfp x)` Returns the next number greater than this one in the direction of x.
`Dfp` | `power10(int e)` Return the specified power of 10.
`Dfp` | `power10K(int e)` Get the specified power of 10000.
`Dfp` | `remainder(Dfp d)` Returns the IEEE remainder.
`Dfp` | `rint()` Round to nearest integer using the round-half-even method.
`protected int` | `round(int n)` Round this given the next digit n using the current rounding mode.
`protected void` | `shiftLeft()` Shift the mantissa left, and adjust the exponent to compensate.
`protected void` | `shiftRight()` Shift the mantissa right, and adjust the exponent to compensate.
`Dfp` | `sqrt()` Compute the square root.
`Dfp` | `subtract(Dfp x)` Subtract x from this.
`double` | `toDouble()` Convert the instance into a double.
`double[]` | `toSplitDouble()` Convert the instance into a split double.
`String` | `toString()` Get a string representation of the instance.
`protected Dfp` | `trap(int type, String what, Dfp oper, Dfp def, Dfp result)` Trap handler.
`protected Dfp` | `trunc(DfpField.RoundingMode rmode)` Does the integer conversions with the specified rounding.
`boolean` | `unequal(Dfp x)` Check if instance is not equal to x.

Methods inherited from class java.lang.Object
`clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

Field Detail

### RADIX

    public static final int RADIX

  The radix, or base of this system. Set to 10000

  See Also:
    Constant Field Values

### MIN_EXP

    public static final int MIN_EXP

  The minimum exponent before underflow is signaled. Flush to zero occurs at minExp-DIGITS

  See Also:
    Constant Field Values

### MAX_EXP

    public static final int MAX_EXP

  The maximum exponent before overflow is signaled and results flushed to infinity

  See Also:
    Constant Field Values

### ERR_SCALE

    public static final int ERR_SCALE

  The amount under/overflows are scaled by before going to trap handler

  See Also:
    Constant Field Values

### FINITE

    public static final byte FINITE

  Indicator value for normal finite numbers.

  See Also:
    Constant Field Values

### INFINITE

    public static final byte INFINITE

  Indicator value for Infinity.

  See Also:
    Constant Field Values

### SNAN

    public static final byte SNAN

  Indicator value for signaling NaN.

  See Also:
    Constant Field Values

### QNAN

    public static final byte QNAN

  Indicator value for quiet NaN.

  See Also:
    Constant Field Values

### mant

    protected int[] mant

  Mantissa.

### sign

    protected byte sign

  Sign bit: & for positive, -1 for negative.

### exp

    protected int exp

  Exponent.

### nans

    protected byte nans

  Indicator for non-finite / non-number values.

Constructor Detail

### Dfp

    protected Dfp(DfpField field)

  Makes an instance with a value of zero.

  Parameters:
    `field` - field to which this instance belongs

### Dfp

    protected Dfp(DfpField field,
                  byte x)

  Create an instance from a byte value.

  Parameters:
    `field` - field to which this instance belongs
    `x` - value to convert to an instance

### Dfp

    protected Dfp(DfpField field,
                  int x)

  Create an instance from an int value.

  Parameters:
    `field` - field to which this instance belongs
    `x` - value to convert to an instance

### Dfp

    protected Dfp(DfpField field,
                  long x)

  Create an instance from a long value.

  Parameters:
    `field` - field to which this instance belongs
    `x` - value to convert to an instance

### Dfp

    protected Dfp(DfpField field,
                  double x)

  Create an instance from a double value.

  Parameters:
    `field` - field to which this instance belongs
    `x` - value to convert to an instance

### Dfp

    public Dfp(Dfp d)

  Copy constructor.

  Parameters:
    `d` - instance to copy

### Dfp

    protected Dfp(DfpField field,
                  String s)

  Create an instance from a String representation.

  Parameters:
    `field` - field to which this instance belongs
    `s` - string representation of the instance

### Dfp

    protected Dfp(DfpField field,
                  byte sign,
                  byte nans)

  Creates an instance with a non-finite value.

  Parameters:
    `field` - field to which this instance belongs
    `sign` - sign of the Dfp to create
    `nans` - code of the value, must be one of `INFINITE`, `SNAN`, `QNAN`

Method Detail

### newInstance

    public Dfp newInstance()

  Create an instance with a value of 0. Use this internally in preference to constructors to facilitate subclasses

  Returns:
    a new instance with a value of 0

### newInstance

    public Dfp newInstance(byte x)

  Create an instance from a byte value.

  Parameters:
    `x` - value to convert to an instance
  Returns:
    a new instance with value x

### newInstance

    public Dfp newInstance(int x)

  Create an instance from an int value.

  Parameters:
    `x` - value to convert to an instance
  Returns:
    a new instance with value x

### newInstance

    public Dfp newInstance(long x)

  Create an instance from a long value.

  Parameters:
    `x` - value to convert to an instance
  Returns:
    a new instance with value x

### newInstance

    public Dfp newInstance(double x)

  Create an instance from a double value.

  Parameters:
    `x` - value to convert to an instance
  Returns:
    a new instance with value x

### newInstance

    public Dfp newInstance(Dfp d)

  Create an instance by copying an existing one. Use this internally in preference to constructors to facilitate subclasses.

  Parameters:
    `d` - instance to copy
  Returns:
    a new instance with the same value as d

### newInstance

    public Dfp newInstance(String s)

  Create an instance from a String representation. Use this internally in preference to constructors to facilitate subclasses.

  Parameters:
    `s` - string representation of the instance
  Returns:
    a new instance parsed from specified string

### newInstance

    public Dfp newInstance(byte sig,
                           byte code)

  Creates an instance with a non-finite value.

  Parameters:
    `sig` - sign of the Dfp to create
    `code` - code of the value, must be one of `INFINITE`, `SNAN`, `QNAN`
  Returns:
    a new instance with a non-finite value

### getField

    public DfpField getField()

  Get the `Field` (really a `DfpField`) to which the instance belongs.

  The field is linked to the number of digits and acts as a factory for `Dfp` instances.

  Specified by:
    `getField` in interface `FieldElement<Dfp>`
  Returns:
    `Field` (really a `DfpField`) to which the instance belongs

### getRadixDigits

    public int getRadixDigits()

  Get the number of radix digits of the instance.

  Returns:
    number of radix digits

### getZero

    public Dfp getZero()

  Get the constant 0.

  Returns:
    a Dfp with value zero

### getOne

    public Dfp getOne()

  Get the constant 1.

  Returns:
    a Dfp with value one

### getTwo

    public Dfp getTwo()

  Get the constant 2.

  Returns:
    a Dfp with value two

### shiftLeft

    protected void shiftLeft()

  Shift the mantissa left, and adjust the exponent to compensate.

### shiftRight

    protected void shiftRight()

  Shift the mantissa right, and adjust the exponent to compensate.

### align

    protected int align(int e)

  Make our exp equal to the supplied one, this may cause rounding. Also causes de-normalized numbers. These numbers are generally dangerous because most routines assume normalized numbers. Align doesn't round, so it will return the last digit destroyed by shifting right.

  Parameters:
    `e` - desired exponent
  Returns:
    last digit destroyed by shifting right

### lessThan

    public boolean lessThan(Dfp x)

  Check if instance is less than x.

  Parameters:
    `x` - number to check instance against
  Returns:
    true if instance is less than x and neither are NaN, false otherwise

### greaterThan

    public boolean greaterThan(Dfp x)

  Check if instance is greater than x.

  Parameters:
    `x` - number to check instance against
  Returns:
    true if instance is greater than x and neither are NaN, false otherwise

### isInfinite

    public boolean isInfinite()

  Check if instance is infinite.

  Returns:
    true if instance is infinite

### isNaN

    public boolean isNaN()

  Check if instance is not a number.

  Returns:
    true if instance is not a number

### equals

    public boolean equals(Object other)

  Check if instance is equal to x.

  Overrides:
    `equals` in class `Object`
  Parameters:
    `other` - object to check instance against
  Returns:
    true if instance is equal to x and neither are NaN, false otherwise

### hashCode

    public int hashCode()

  Gets a hashCode for the instance.

  Overrides:
    `hashCode` in class `Object`
  Returns:
    a hash code value for this object

### unequal

    public boolean unequal(Dfp x)

  Check if instance is not equal to x.

  Parameters:
    `x` - number to check instance against
  Returns:
    true if instance is not equal to x and neither are NaN, false otherwise

### rint

    public Dfp rint()

  Round to nearest integer using the round-half-even method. That is round to nearest integer unless both are equidistant. In which case round to the even one.

  Returns:
    rounded value

### floor

    public Dfp floor()

  Round to an integer using the round floor mode. That is, round toward -Infinity

  Returns:
    rounded value

### ceil

    public Dfp ceil()

  Round to an integer using the round ceil mode. That is, round toward +Infinity

  Returns:
    rounded value

### remainder

    public Dfp remainder(Dfp d)

  Returns the IEEE remainder.

  Parameters:
    `d` - divisor
  Returns:
    this less n × d, where n is the integer closest to this/d

### trunc

    protected Dfp trunc(DfpField.RoundingMode rmode)

  Does the integer conversions with the specified rounding.

  Parameters:
    `rmode` - rounding mode to use
  Returns:
    truncated value

### intValue

    public int intValue()

  Convert this to an integer. If greater than 2147483647, it returns 2147483647. If less than -2147483648 it returns -2147483648.

  Returns:
    converted number

### log10K

    public int log10K()

  Get the exponent of the greatest power of 10000 that is less than or equal to the absolute value of this. I.E. if this is 106 then log10K would return 1.

  Returns:
    integer base 10000 logarithm

### power10K

    public Dfp power10K(int e)

  Get the specified power of 10000.

  Parameters:
    `e` - desired power
  Returns:
    10000e

### log10

    public int log10()

  Get the exponent of the greatest power of 10 that is less than or equal to abs(this).

  Returns:
    integer base 10 logarithm

### power10

    public Dfp power10(int e)

  Return the specified power of 10.

  Parameters:
    `e` - desired power
  Returns:
    10e

### complement

    protected int complement(int extra)

  Negate the mantissa of this by computing the complement. Leaves the sign bit unchanged, used internally by add. Denormalized numbers are handled properly here.

  Parameters:
    `extra` - ???
  Returns:
    ???

### add

    public Dfp add(Dfp x)

  Add x to this.

  Specified by:
    `add` in interface `FieldElement<Dfp>`
  Parameters:
    `x` - number to add
  Returns:
    sum of this and x

### negate

    public Dfp negate()

  Returns a number that is this number with the sign bit reversed.

  Returns:
    the opposite of this

### subtract

    public Dfp subtract(Dfp x)

  Subtract x from this.

  Specified by:
    `subtract` in interface `FieldElement<Dfp>`
  Parameters:
    `x` - number to subtract
  Returns:
    difference of this and a

### round

    protected int round(int n)

  Round this given the next digit n using the current rounding mode.

  Parameters:
    `n` - ???
  Returns:
    the IEEE flag if an exception occurred

### multiply

    public Dfp multiply(Dfp x)

  Multiply this by x.

  Specified by:
    `multiply` in interface `FieldElement<Dfp>`
  Parameters:
    `x` - multiplicand
  Returns:
    product of this and x

### multiply

    public Dfp multiply(int x)

  Multiply this by a single digit 0<=x<radix. There are speed advantages in this special case

  Parameters:
    `x` - multiplicand
  Returns:
    product of this and x

### divide

    public Dfp divide(Dfp divisor)

  Divide this by divisor.

  Specified by:
    `divide` in interface `FieldElement<Dfp>`
  Parameters:
    `divisor` - divisor
  Returns:
    quotient of this by divisor

### divide

    public Dfp divide(int divisor)

  Divide by a single digit less than radix. Special case, so there are speed advantages. 0 <= divisor < radix

  Parameters:
    `divisor` - divisor
  Returns:
    quotient of this by divisor

### sqrt

    public Dfp sqrt()

  Compute the square root.

  Returns:
    square root of the instance

### toString

    public String toString()

  Get a string representation of the instance.

  Overrides:
    `toString` in class `Object`
  Returns:
    string representation of the instance

### dfp2sci

    protected String dfp2sci()

  Convert an instance to a string using scientific notation.

  Returns:
    string representation of the instance in scientific notation

### dfp2string

    protected String dfp2string()

  Convert an instance to a string using normal notation.

  Returns:
    string representation of the instance in normal notation

### dotrap

    public Dfp dotrap(int type,
                      String what,
                      Dfp oper,
                      Dfp result)

  Raises a trap. This does not set the corresponding flag however.

  Parameters:
    `type` - the trap type
    `what` - - name of routine trap occurred in
    `oper` - - input operator to function
    `result` - - the result computed prior to the trap
  Returns:
    The suggested return value from the trap handler

### trap

    protected Dfp trap(int type,
                       String what,
                       Dfp oper,
                       Dfp def,
                       Dfp result)

  Trap handler. Subclasses may override this to provide trap functionality per IEEE 854-1987.

  Parameters:
    `type` - The exception type - e.g. FLAG_OVERFLOW
    `what` - The name of the routine we were in e.g. divide()
    `oper` - An operand to this function if any
    `def` - The default return value if trap not enabled
    `result` - The result that is specified to be delivered per IEEE 854, if any
  Returns:
    the value that should be return by the operation triggering the trap

### classify

    public int classify()

  Returns the type - one of FINITE, INFINITE, SNAN, QNAN.

  Returns:
    type of the number

### copysign

    public static Dfp copysign(Dfp x,
                               Dfp y)

  Creates an instance that is the same as x except that it has the sign of y. abs(x) = dfp.copysign(x, dfp.one)

  Parameters:
    `x` - number to get the value from
    `y` - number to get the sign from
  Returns:
    a number with the value of x and the sign of y

### nextAfter

    public Dfp nextAfter(Dfp x)

  Returns the next number greater than this one in the direction of x. If this==x then simply returns this.

  Parameters:
    `x` - direction where to look at
  Returns:
    closest number next to instance in the direction of x

### toDouble

    public double toDouble()

  Convert the instance into a double.

  Returns:
    a double approximating the instance
  See Also:
    `toSplitDouble()`

### toSplitDouble

    public double[] toSplitDouble()

  Convert the instance into a split double.

  Returns:
    an array of two doubles which sum represent the instance
  See Also:
    `toDouble()`

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