Merge pull request #7 from seberg/mpfdtype

ENH: Add my "MPFR" example

Author: ngoldbaum

mpfdtype/.gitignore

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+dist/
+.mesonpy*.ini
+__pycache__

mpfdtype/README.md

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+# A multi precision DType for NumPy
+
+:warning: Note that while the DType is BSD license, MPFR and GMP which it
+must be linked with are not.
+
+A very basic example::
+
+    import numpy as np
+    from mpfdtype import MPFDType, MPFloat
+
+    # create an array with 200 bits precision:
+    arr = np.arange(3).astype(MPFDType(200))
+    print(repr(arr))
+    # array(['0E+00', '1.0E+00', '2.0E+00'], dtype=MPFDType(200))
+
+    # Math uses the input precision (wraps almost all math functions):
+    res = arr**2 + np.sqrt(arr)
+    print(repr(res))
+    # array(['0E+00', '2.0E+00',
+    #        '5.4142135623730950488016887242096980785696718753769480731766784E+00'],
+    #       dtype=MPFDType(200))
+
+    # cast to a different precision:
+    arr2 = arr.astype(MPFDType(500))
+    print(repr(arr2))
+    # array(['0E+00', '1.0E+00', '2.0E+00'], dtype=MPFDType(500))
+
+    res = arr + arr2
+    print(repr(res))  # uses the larger precision now
+    # array(['0E+00', '2.0E+00', '4.0E+00'], dtype=MPFDType(500))
+
+There also is an `mpf.MPFloat(value, prec=None)`.  There is no "context"
+as most libraries like this (including mpfr itself) typically have.
+The rounding mode is always the normal one.

mpfdtype/meson.build

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+project(
+  'mpfdtype',
+  'c',
+  'cpp',
+)
+
+py_mod = import('python')
+py = py_mod.find_installation()
+
+c = meson.get_compiler('c')
+mpfr = c.find_library('mpfr')
+
+incdir_numpy = run_command(py,
+  [
+    '-c',
+    'import numpy; print(numpy.get_include())'
+  ],
+  check: true
+).stdout().strip()
+
+includes = include_directories(
+  [
+    incdir_numpy,
+    'mpfdtype/src',
+  ],
+)
+
+srcs = [
+  'mpfdtype/src/casts.cpp',
+  'mpfdtype/src/casts.h',
+  'mpfdtype/src/dtype.c',
+  'mpfdtype/src/dtype.h',
+  'mpfdtype/src/mpfdtype_main.c',
+  'mpfdtype/src/numbers.cpp',
+  'mpfdtype/src/numbers.h',
+  'mpfdtype/src/ops.hpp',
+  'mpfdtype/src/scalar.c',
+  'mpfdtype/src/scalar.h',
+  'mpfdtype/src/terrible_hacks.c',
+  'mpfdtype/src/terrible_hacks.h',
+  'mpfdtype/src/umath.cpp',
+  'mpfdtype/src/umath.h',
+]
+
+py.install_sources(
+  [
+    'mpfdtype/__init__.py',
+  ],
+  subdir: 'mpfdtype'
+)
+
+py.extension_module(
+  '_mpfdtype_main',
+  srcs,
+  install: true,
+  subdir: 'mpfdtype',
+  include_directories: includes,
+  dependencies: [mpfr],
+)

mpfdtype/mpfdtype/__init__.py

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+import numpy as np
+
+from ._mpfdtype_main import MPFDType, MPFloat
+
+
+
+# Lets add some uglier hacks:
+
+# NumPy uses repr as a fallback (as of writing this code), we want to
+# customize the printing of MPFloats though...
+def mystr(obj):
+    if isinstance(obj, MPFloat):
+        return f"'{obj}'"
+    return repr(obj)
+
+np.set_printoptions(formatter={"numpystr": mystr})