[PATCH v4 0/2] Introduce decimal type to tarantool core.

[Serge Petrenko <sergepetrenko@tarantool.org>]

This patchset adds a new type, decimal fixed-point, to tarantool,
together with methods to pack/unpack decimals, arithmetic operations
ad math functions.

The first patch adds decNumber library as a submodule.

The second patch adds a small wrapper to the library to make it work
with fixed-point decimal values, and adds a unit test.
To evaluate number precision and scale from exponent and the amount of
significant digits the following formulas are applied:
If exponent < 0 then precision = MAX(digits, -exponent) and scale = -exponent
If exponent > 0 then precision = digits + exponent, and scale = 0

Changes in v4:
 - review fixes as per review
   from @locker.
 - remove patches 3 and 4,
   add decimal_pack/unpack as
   a preparation for patches
   4 and 4 to patch 2.

Changes in v3:
 - add patches 3 and 4 to
   encode/decode decimals
   as msgpack.

Changes in v2:
 - get rid of explicit precision and scale,
   evaluate them from decNumber digits and exponent.
 - decimal is now an alias for decNumber
 - ln, log10, exp, sqrt, pow now accept precision to
   which the result should be rounded.

Serge Petrenko (2):
  third-party: add decNumber library
  lib/core: introduce decimal type to tarantool

 .gitmodules                 |   3 +
 CMakeLists.txt              |   7 +
 cmake/BuildDecNumber.cmake  |  14 ++
 src/CMakeLists.txt          |   1 +
 src/lib/core/CMakeLists.txt |   3 +-
 src/lib/core/decimal.c      | 354 +++++++++++++++++++++++++++++++
 src/lib/core/decimal.h      | 206 ++++++++++++++++++
 test/unit/CMakeLists.txt    |   2 +
 test/unit/decimal.c         | 174 ++++++++++++++++
 test/unit/decimal.result    | 406 ++++++++++++++++++++++++++++++++++++
 third_party/decNumber       |   1 +
 11 files changed, 1170 insertions(+), 1 deletion(-)
 create mode 100644 cmake/BuildDecNumber.cmake
 create mode 100644 src/lib/core/decimal.c
 create mode 100644 src/lib/core/decimal.h
 create mode 100644 test/unit/decimal.c
 create mode 100644 test/unit/decimal.result
 create mode 160000 third_party/decNumber

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2.20.1 (Apple Git-117)