Sisyphus > Math-Decimal64-0.05 > Math::Decimal64

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NAME ^

Math::Decimal64 - (alpha) perl interface to C's _Decimal64 operations.

DEPENDENCIES ^

   In order to compile this module, a C compiler that provides
   the _Decimal64 type is needed.

DESCRIPTION ^

   Note that this module is alpha software. It seems to work ok
   for me on Windows 7 (Intel processor,compiling with gcc-4.6.3,
   gcc-4.7.0) and Ubuntu-12.04LTS (Amd64 processor, gcc-4.6.3).

   It also works for me on Debian wheezy (PowerpC processor,
   gcc-4.6.3) apart from caveats mentioned in the docs below.

   Math::Decimal64 supports up to 16 decimal digits of significand
   (mantissa) and an exponent range of -383 to +384.
   The smallest expressable value is -9.999999999999999e384 (which
   is also equivalent to -9999999999999999e369).
   The largest expressable value is 9.999999999999999e384 (which
   also equivalent to 9999999999999999e369).
   The closest we can get to zero is (plus or minus) 1e-384
   (which is also equivalent to 1000000000000000e-399).

   This module allows decimal floating point arithmetic via
   operator overloading - see "OVERLOADING".

   In the documentation that follows, "$mantissa" is a perl scalar
   holding a string of up to 16 decimal digits:
    $mantissa = '1234';
    $mantissa = '1234567890123456';

   For many values, it normally shouldn't matter if $mantissa is 
   assigned as a number:
    $mantissa = 1234;      # should work ok.

   But on some perls there are values that *need* to be assigned
   as a string. For example, on perls where nvtype is an 8 byte
   'double':
    $mantissa = '-9307199254740993'; # works fine
    $mantissa = -9307199254740993;   # will assign wrong value

   So ... where you see "$mantissa" in the following docs, think
   *string* of up to 16 decimal digits".

SYNOPSIS ^

   use Math::Decimal64 qw(:all);

   my $d64_1 = MEtoD64('9927', -2); # the decimal 99.27
   my $d64_2 = MEtoD64('3', 0);     # the decimal 3.0
   $d64_1 /= $d64_2;
   print $d64_1; # prints 3309e-2 (33.09)

OVERLOADING ^

   The following operations are overloaded:
    + - * /
    += -= *= /=
    != == <= >= <=> < >
    ++ --
    =
    abs bool int print

    Arguments to the overloaded operations must be Math::Decimal64
    objects or integer (IV/UV) values.

    If your perl has 8-byte (or larger) IV/UV, then you may get
    unexpected results if you pass an IV/UV to the overloaded
    operators (because the precision of the IV/UV exceeds the
    precision of the _Decimal64 type) - it depends upon just how
    big the absolute value of the IV/UV is.

     $d64_2 = $d64_1 + 15; # ok

     $d64_2 = $d64_1 + 3.1; # Error. Best to either:
     $d64_2 = $d64_1 + MEtoD64('31',-1); # or (equivalentally):
     $d64_2 = $d64_1 + Math::Decimal64->new('31',-1);

CREATION & ASSIGNMENT FUNCTIONS ^

    The following create and assign a new Math::Decimal64 object.

     ###################################
     # Assign from mantissa and exponent
     $d64 = MEtoD64($mantissa, $exponent);
       
      eg: $d64 = MEtoD64('12345', -3); # 12.345
    
      It's a little kludgy, but this is the safest and surest way
      of creating the Math::Decimal64 object with the intended
      value.
      Checks are conducted to ensure that the arguments are suitable.
      The mantissa string must represent an integer. (There's an 
      implicit '.0' at the end of the string.)
      Only known caveat is that, since this function does a strtold()
      on the mantissa, the 'long double' needs to have at least 55
      bits of precision.
      Doing Math::Decimal64->new($mantissa, $exponent) will also
      create and assign using MEtoD64(), and is equally acceptable.

     ######################
     # Assign from a string
     $d64 = PVtoD64($string);

      eg: $d64 = PVtoD64('-9427199254740993');
          $d64 = PVtoD64('-9307199254740993e-15');
          $d64 = Math::Decimal64->new('-9787199254740993');
          $d64 = Math::Decimal64->new('-9307199254740993e-23');

      Does no checks on its arg. The arg can be in either integer 
      format or scientific notation or float format.
      Doing Math::Decimal64->new($string) will also create and
      assign using PVtoD64().
      This assigns using the C standard library function strtold(),
      and then casting to a _Decimal64.
      It is significantly faster than MEtoD64 for exponents outside
      the range (-10 .. 10) and I think it is reliable so long as:
       1) the 'long double' type has precision of 55 bits or more;
       2) the 'long double' type accommodates the _Decimal64 type's
          exponent range;
       3) Any (and all) digits after the mantissa's 16th digit 
          are '0'.

     #####################################
     # Assign from a UV (unsigned integer)
     $d64 = UVtoD64($uv);

      eg: $d64 = UVtoD64(~0);

      Doing Math::Decimal64->new($uv) will also create and assign
      using UVtoD64().
      On perls where the UV is 8 bytes or larger, the precision of
      the UV exceeds the precision of the _Decimal64 - and this
      function is not therefore recommended on such perls (unless
      you're sure the UV value won't be subject to rounding).
      Check the size of the UV by running perl -V:ivsize

     ####################################
     # Assign from an IV (signed integer)
     $d64 = IVtoD64($iv);

      eg: $d64 = IVtoD64(-15); # -15.0
      
      Doing Math::Decimal64->new($iv) will also create and assign
      using IVtoD64().
      On perls where the IV is 8 bytes or larger, the precision of
      the UV exceeds the precision of the _Decimal64 - and this
      function is not therefore recommended on such perls (unless
      you're sure the IV value won't be subject to rounding).
      Check the size of the IV by running perl -V:ivsize

     ################################################
     # Assign from an existing Math::Decimal64 object
     $d64 = D64toD64($d64_0);
     Also:
      $d64 = Math::Decimal64->new($d64_0);
      $d64 = $d64_0; # uses overloaded '='

     ###########################
     # Assign from an NV (real))
     $d64 = NVtoD64($nv);

      eg: $d64 = NVtoD64(-3.25);

      Doing Math::Decimal64->new($nv) will also create and assign
      using NVtoD64().
      Might not always assign the value you think it does. (Eg,
      see test 5 in t/overload_cmp.t.)

     ####################
     # Assign using new()
     $d64 = Math::Decimal64->new([$arg1, [$arg2]]);
      This function calls one of the above functions. It
      determines the appropriate function to call by examining
      the argument(s) provided.
      If no argument is provided, a Math::Decimal64 object
      with a value of NaN is returned.
      If 2 arguments are supplied it uses MEtoD64().
      If one argument is provided, that arg's internal flags are
      used to determine the appropriate function to call.

     #######################
     # Assign using STRtoD64
     $d64 = STRtoD64($string);
      If your C compiler provides the strtod64 function, and
      you configured the Makefile.PL to enable access to that
      function then you can use this function. 
      usage is is as for PVtoD64().

     ##############################

ASSIGN A NEW VALUE TO AN EXISTING OBJECT ^

     assignME($d64, $mantissa, $exponent);
      Assigns the value represented by ($mantissa, $exponent)
      to the Math::Decimal64 object, $d64.
      Performs same argument checking as MEtoD64.
      Same caveats apply here as to MEtoD64 - see the MEtoD64
      documentation.

      eg: assignME($d64, '123459', -6); # 0.123459

     assignPV($d64, $string);
      Assigns the value represented by $string to the 
      Math::Decimal64 object, $d64.
      Doesn't check to see what $string contains.
      Same caveats apply here as to PVtoD64() - see the PVtoD64
      documentation (above).

      eg: assignPV($d64, '123459e-6'); # 0.123459

     assignNaN($d64);
      Assigns a NaN to the Math::Decimal64 object, $d64.

     assignInf($d64, $sign);
      Assigns an Inf to the Math::Decimal64 object, $d64.
      If $sign is negative, assigns -Inf; otherwise +Inf.

INF, NAN and ZERO OBJECTS ^

     $d64 = InfD64($sign);
      If $sign < 0, creates a new Math::Decimal64 object set to
      negative infinity; else creates a Math::Decimal64 object set
      to positive infinity.

     $d64 = NaND64();
      Creates a new Math::Decimal64 object set to NaN.
      Same as "$d64 = Math::Decimal64->new();"

     $d64 = ZeroD64($sign);
      If $sign < 0, creates a new Math::Decimal64 object set to
      negative zero; else creates a Math::Decimal64 object set to 
      zero.

RETRIEVAL FUNCTIONS ^

    The following functions provide ways of seeing the value of
    Math::Decimal64 objects.

     ($mantissa, $exponent) = D64toME($d64);
      Returns the value of the Math::Decimal object as a 
      mantissa (string of up to 16 decimal digits) and exponent.
      You can then manipulate those values to output the
      value in your preferred format. Afaik, the value will be
      translated accurately.

     ($mantissa, $exponent) = FR64toME($d64);
      Requires that Math::MPFR version 3.18 or later has been
      loaded. It also requires that Math:MPFR has been built with
      support for the mpfr library's Decimal64 conversion
      functions - in which case Math::MPFR::_WANT_DECIMAL_FLOATS()
      will return true. (Otherwise it returns false.)
      Afaik, the value will be translated accurately.

     $nv = D64toNV($d64);
      This function returns the value of the Math::Decimal64
      object to a perl scalar (NV). Under certain conditions
      it may not translate the value accurately.

     print $d64;
      Will print the value in the format (eg) -12345e-2, which
      equates to the decimal -123.45. Uses D64toME().

     pFR $d64;
      Will print the value in the format (eg) -12345e-2, which
      equates to the decimal -123.45. Uses FR64toME() - which
      should always print the value accurately, but requires
      that Math::MPFR:
       1) has been loaded;
       2) supports the Decimal64 mpfr conversion functions.

OTHER FUNCTIONS $d64 = DEC64_MAX; # 9999999999999999e369 $d64 = DEC64_MIN; # 1e-398 DEC64_MAX is the largest positive finite representable _Decimal64 value. DEC64_MIN is the smallest positive non-zero representable _Decimal64 value. Multiply these by -1 to get their negative counterparts. ^

     $d64 = Exp10($pow);
      Returns a Math::Decimal64 object with a value of
      10 ** $pow, for $pow in the range (-398 .. 384). Croaks
      with appropriate message if $pow is not within that range.

     $bool = have_strtod64();
      Returns true if, when building Math::Decimal64,
      the Makefile.PL was configured to make the STRtoD64()
      function available for your build of Math::Decimal64. Else
      returns false.
      (No use making this function available if your compiler's
      C library doesn't provide the strtod64 function.)
      

     $test = is_ZeroD64($d64);
      Returns:
       -1 if $d64 is negative zero;
        1 if $d64 is a positive zero;
        0 if $d64 is not zero.

     $test = is_InfD64($d64);
      Returns:
       -1 if $d64 is negative infinity;
        1 if $d64 is positive infinity;
        0 if $d64 is not infinity.

     $bool = is_NaND64($d64);
      Returns:
        1 if $d64 is a NaN;
        0 if $d64 is not a NaN.

     LDtoD64($d64, $ld); # $ld is a Math::LongDouble object
     D64toLD($ld, $d64); # $ld is a Math::LongDouble object

     Conversions between Math::LongDouble and Math::Decimal64
     objects - done by simply casting the long double value to a
     _Decimal64 value, or (resp.) vice-versa.
     Requires that Math::LongDouble has been loaded.

LICENSE ^

    This program is free software; you may redistribute it and/or 
    modify it under the same terms as Perl itself.
    Copyright 2012-13 Sisyphus

AUTHOR ^

    Sisyphus <sisyphus at(@) cpan dot (.) org>
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