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planar / lib / planar / __init__.py

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#############################################################################
# Copyright (c) 2010 by Casey Duncan
# Portions copyright (c) 2009 The Super Effective Team 
#                             (www.supereffective.org)
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
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# * Redistributions of source code must retain the above copyright notice, 
#   this list of conditions and the following disclaimer.
# * Redistributions in binary form must reproduce the above copyright notice,
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"""2d planar geometry library for Python"""

__all__ = ('TransformNotInvertibleError', 'set_epsilon', 
    'Vec2', 'Point', 'Vec2Array', 'Seq2', 
    'Line', 'Ray', 'LineSegment',
    'Affine', 'BoundingBox', 'Polygon')

__versioninfo__ = (0, 3, 0)
__version__ = '.'.join(str(n) for n in __versioninfo__)

try: # pragma: no cover
    # Default to C implementation
    from planar.c import _set_epsilon, Vec2, Vec2Array, Seq2, Affine, \
        BoundingBox, Polygon, TransformNotInvertibleError

    __implementation__ = 'C'
except ImportError: # pragma: no cover
    # Fall-back to Python implementation
    from planar.py import Vec2, Vec2Array, Seq2, Affine, \
        Line, Ray, LineSegment, BoundingBox, Polygon

    class TransformNotInvertibleError(Exception):
        """The transform could not be inverted"""

    def _set_epsilon(e): pass

    __implementation__ = 'Python'

Point = Vec2
"""``Point`` is an alias for ``Vec2``. 
Use ``Point`` where desired for clarity in your code.
"""

def set_epsilon(epsilon):
    """Set the global absolute error value and rounding limit for approximate
    floating point comparison operations. This value is accessible via the
    :attr:`planar.EPSILON` global variable.

    The default value of ``0.00001`` is suitable for values
    that are in the "countable range". You may need a larger
    epsilon when using large absolute values, and a smaller value
    for very small values close to zero. Otherwise approximate
    comparison operations will not behave as expected.
    """
    global EPSILON, EPSILON2
    EPSILON = float(epsilon)
    EPSILON2 = EPSILON**2
    _set_epsilon(EPSILON)

set_epsilon(1e-5)


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