1 # Copyright (c) 2007, Robert Coup <robert.coup@onetrackmind.co.nz>

     2 # All rights reserved.

     3 #

     4 # Redistribution and use in source and binary forms, with or without modification,

     5 # are permitted provided that the following conditions are met:

     6 #

     7 #   1. Redistributions of source code must retain the above copyright notice,

     8 #      this list of conditions and the following disclaimer.

     9 #

    10 #   2. Redistributions in binary form must reproduce the above copyright

    11 #      notice, this list of conditions and the following disclaimer in the

    12 #      documentation and/or other materials provided with the distribution.

    13 #

    14 #   3. Neither the name of Distance nor the names of its contributors may be used

    15 #      to endorse or promote products derived from this software without

    16 #      specific prior written permission.

    17 #

    18 # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND

    19 # ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

    20 # WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE

    21 # DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR

    22 # ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES

    23 # (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;

    24 # LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON

    25 # ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

    26 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS

    27 # SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

    28 #

    29 """

    30 Distance and Area objects to allow for sensible and convienient calculation

    31 and conversions.

    32 

    33 Authors: Robert Coup, Justin Bronn

    34 

    35 Inspired by GeoPy (http://exogen.case.edu/projects/geopy/)

    36 and Geoff Biggs' PhD work on dimensioned units for robotics.

    37 """

    38 __all__ = ['A', 'Area', 'D', 'Distance']

    39 from decimal import Decimal

    40 

    41 class MeasureBase(object):

    42     def default_units(self, kwargs):

    43         """

    44         Return the unit value and the default units specified

    45         from the given keyword arguments dictionary.

    46         """

    47         val = 0.0

    48         for unit, value in kwargs.iteritems():

    49             if not isinstance(value, float): value = float(value)

    50             if unit in self.UNITS:

    51                 val += self.UNITS[unit] * value

    52                 default_unit = unit

    53             elif unit in self.ALIAS:

    54                 u = self.ALIAS[unit]

    55                 val += self.UNITS[u] * value

    56                 default_unit = u

    57             else:

    58                 lower = unit.lower()

    59                 if lower in self.UNITS:

    60                     val += self.UNITS[lower] * value

    61                     default_unit = lower

    62                 elif lower in self.LALIAS:

    63                     u = self.LALIAS[lower]

    64                     val += self.UNITS[u] * value

    65                     default_unit = u

    66                 else:

    67                     raise AttributeError('Unknown unit type: %s' % unit)

    68         return val, default_unit

    69 

    70     @classmethod

    71     def unit_attname(cls, unit_str):

    72         """

    73         Retrieves the unit attribute name for the given unit string.

    74         For example, if the given unit string is 'metre', 'm' would be returned.

    75         An exception is raised if an attribute cannot be found.

    76         """

    77         lower = unit_str.lower()

    78         if unit_str in cls.UNITS:

    79             return unit_str

    80         elif lower in cls.UNITS:

    81             return lower

    82         elif lower in cls.LALIAS:

    83             return cls.LALIAS[lower]

    84         else:

    85             raise Exception('Could not find a unit keyword associated with "%s"' % unit_str)

    86 

    87 class Distance(MeasureBase):

    88     UNITS = {

    89         'chain' : 20.1168,

    90         'chain_benoit' : 20.116782,

    91         'chain_sears' : 20.1167645,

    92         'british_chain_benoit' : 20.1167824944,

    93         'british_chain_sears' : 20.1167651216,

    94         'british_chain_sears_truncated' : 20.116756,

    95         'cm' : 0.01,

    96         'british_ft' : 0.304799471539,

    97         'british_yd' : 0.914398414616,

    98         'clarke_ft' : 0.3047972654,

    99         'clarke_link' : 0.201166195164,

   100         'fathom' :  1.8288,

   101         'ft': 0.3048,

   102         'german_m' : 1.0000135965,

   103         'gold_coast_ft' : 0.304799710181508,

   104         'indian_yd' : 0.914398530744,

   105         'inch' : 0.0254,

   106         'km': 1000.0,

   107         'link' : 0.201168,

   108         'link_benoit' : 0.20116782,

   109         'link_sears' : 0.20116765,

   110         'm': 1.0,

   111         'mi': 1609.344,

   112         'mm' : 0.001,

   113         'nm': 1852.0,

   114         'nm_uk' : 1853.184,

   115         'rod' : 5.0292,

   116         'sears_yd' : 0.91439841,

   117         'survey_ft' : 0.304800609601,

   118         'um' : 0.000001,

   119         'yd': 0.9144,

   120         }

   121 

   122     # Unit aliases for `UNIT` terms encountered in Spatial Reference WKT.

   123     ALIAS = {

   124         'centimeter' : 'cm',

   125         'foot' : 'ft',

   126         'inches' : 'inch',

   127         'kilometer' : 'km',

   128         'kilometre' : 'km',

   129         'meter' : 'm',

   130         'metre' : 'm',

   131         'micrometer' : 'um',

   132         'micrometre' : 'um',

   133         'millimeter' : 'mm',

   134         'millimetre' : 'mm',

   135         'mile' : 'mi',

   136         'yard' : 'yd',

   137         'British chain (Benoit 1895 B)' : 'british_chain_benoit',

   138         'British chain (Sears 1922)' : 'british_chain_sears',

   139         'British chain (Sears 1922 truncated)' : 'british_chain_sears_truncated',

   140         'British foot (Sears 1922)' : 'british_ft',

   141         'British foot' : 'british_ft',

   142         'British yard (Sears 1922)' : 'british_yd',

   143         'British yard' : 'british_yd',

   144         "Clarke's Foot" : 'clarke_ft',

   145         "Clarke's link" : 'clarke_link',

   146         'Chain (Benoit)' : 'chain_benoit',

   147         'Chain (Sears)' : 'chain_sears',

   148         'Foot (International)' : 'ft',

   149         'German legal metre' : 'german_m',

   150         'Gold Coast foot' : 'gold_coast_ft',

   151         'Indian yard' : 'indian_yd',

   152         'Link (Benoit)': 'link_benoit',

   153         'Link (Sears)': 'link_sears',

   154         'Nautical Mile' : 'nm',

   155         'Nautical Mile (UK)' : 'nm_uk',

   156         'US survey foot' : 'survey_ft',

   157         'U.S. Foot' : 'survey_ft',

   158         'Yard (Indian)' : 'indian_yd',

   159         'Yard (Sears)' : 'sears_yd'

   160         }

   161     LALIAS = dict([(k.lower(), v) for k, v in ALIAS.items()])

   162 

   163     def __init__(self, default_unit=None, **kwargs):

   164         # The base unit is in meters.

   165         self.m, self._default_unit = self.default_units(kwargs)

   166         if default_unit and isinstance(default_unit, str):

   167             self._default_unit = default_unit

   168 

   169     def __getattr__(self, name):

   170         if name in self.UNITS:

   171             return self.m / self.UNITS[name]

   172         else:

   173             raise AttributeError('Unknown unit type: %s' % name)

   174 

   175     def __repr__(self):

   176         return 'Distance(%s=%s)' % (self._default_unit, getattr(self, self._default_unit))

   177 

   178     def __str__(self):

   179         return '%s %s' % (getattr(self, self._default_unit), self._default_unit)

   180 

   181     def __cmp__(self, other):

   182         if isinstance(other, Distance):

   183             return cmp(self.m, other.m)

   184         else:

   185             return NotImplemented

   186 

   187     def __add__(self, other):

   188         if isinstance(other, Distance):

   189             return Distance(default_unit=self._default_unit, m=(self.m + other.m))

   190         else:

   191             raise TypeError('Distance must be added with Distance')

   192 

   193     def __iadd__(self, other):

   194         if isinstance(other, Distance):

   195             self.m += other.m

   196             return self

   197         else:

   198             raise TypeError('Distance must be added with Distance')

   199 

   200     def __sub__(self, other):

   201         if isinstance(other, Distance):

   202             return Distance(default_unit=self._default_unit, m=(self.m - other.m))

   203         else:

   204             raise TypeError('Distance must be subtracted from Distance')

   205 

   206     def __isub__(self, other):

   207         if isinstance(other, Distance):

   208             self.m -= other.m

   209             return self

   210         else:

   211             raise TypeError('Distance must be subtracted from Distance')

   212 

   213     def __mul__(self, other):

   214         if isinstance(other, (int, float, long, Decimal)):

   215             return Distance(default_unit=self._default_unit, m=(self.m * float(other)))

   216         elif isinstance(other, Distance):

   217             return Area(default_unit='sq_' + self._default_unit, sq_m=(self.m * other.m))

   218         else:

   219             raise TypeError('Distance must be multiplied with number or Distance')

   220 

   221     def __imul__(self, other):

   222         if isinstance(other, (int, float, long, Decimal)):

   223             self.m *= float(other)

   224             return self

   225         else:

   226             raise TypeError('Distance must be multiplied with number')

   227 

   228     def __rmul__(self, other):

   229         return self * other

   230 

   231     def __div__(self, other):

   232         if isinstance(other, (int, float, long, Decimal)):

   233             return Distance(default_unit=self._default_unit, m=(self.m / float(other)))

   234         else:

   235             raise TypeError('Distance must be divided with number')

   236 

   237     def __idiv__(self, other):

   238         if isinstance(other, (int, float, long, Decimal)):

   239             self.m /= float(other)

   240             return self

   241         else:

   242             raise TypeError('Distance must be divided with number')

   243 

   244     def __nonzero__(self):

   245         return bool(self.m)

   246 

   247 class Area(MeasureBase):

   248     # Getting the square units values and the alias dictionary.

   249     UNITS = dict([('sq_%s' % k, v ** 2) for k, v in Distance.UNITS.items()])

   250     ALIAS = dict([(k, 'sq_%s' % v) for k, v in Distance.ALIAS.items()])

   251     LALIAS = dict([(k.lower(), v) for k, v in ALIAS.items()])

   252 

   253     def __init__(self, default_unit=None, **kwargs):

   254         self.sq_m, self._default_unit = self.default_units(kwargs)

   255         if default_unit and isinstance(default_unit, str):

   256             self._default_unit = default_unit

   257 

   258     def __getattr__(self, name):

   259         if name in self.UNITS:

   260             return self.sq_m / self.UNITS[name]

   261         else:

   262             raise AttributeError('Unknown unit type: ' + name)

   263 

   264     def __repr__(self):

   265         return 'Area(%s=%s)' % (self._default_unit, getattr(self, self._default_unit))

   266 

   267     def __str__(self):

   268         return '%s %s' % (getattr(self, self._default_unit), self._default_unit)

   269 

   270     def __cmp__(self, other):

   271         if isinstance(other, Area):

   272             return cmp(self.sq_m, other.sq_m)

   273         else:

   274             return NotImplemented

   275 

   276     def __add__(self, other):

   277         if isinstance(other, Area):

   278             return Area(default_unit=self._default_unit, sq_m=(self.sq_m + other.sq_m))

   279         else:

   280             raise TypeError('Area must be added with Area')

   281 

   282     def __iadd__(self, other):

   283         if isinstance(other, Area):

   284             self.sq_m += other.sq_m

   285             return self

   286         else:

   287             raise TypeError('Area must be added with Area')

   288 

   289     def __sub__(self, other):

   290         if isinstance(other, Area):

   291             return Area(default_unit=self._default_unit, sq_m=(self.sq_m - other.sq_m))

   292         else:

   293             raise TypeError('Area must be subtracted from Area')

   294 

   295     def __isub__(self, other):

   296         if isinstance(other, Area):

   297             self.sq_m -= other.sq_m

   298             return self

   299         else:

   300             raise TypeError('Area must be subtracted from Area')

   301 

   302     def __mul__(self, other):

   303         if isinstance(other, (int, float, long, Decimal)):

   304             return Area(default_unit=self._default_unit, sq_m=(self.sq_m * float(other)))

   305         else:

   306             raise TypeError('Area must be multiplied with number')

   307 

   308     def __imul__(self, other):

   309         if isinstance(other, (int, float, long, Decimal)):

   310             self.sq_m *= float(other)

   311             return self

   312         else:

   313             raise TypeError('Area must be multiplied with number')

   314 

   315     def __rmul__(self, other):

   316         return self * other

   317 

   318     def __div__(self, other):

   319         if isinstance(other, (int, float, long, Decimal)):

   320             return Area(default_unit=self._default_unit, sq_m=(self.sq_m / float(other)))

   321         else:

   322             raise TypeError('Area must be divided with number')

   323 

   324     def __idiv__(self, other):

   325         if isinstance(other, (int, float, long, Decimal)):

   326             self.sq_m /= float(other)

   327             return self

   328         else:

   329             raise TypeError('Area must be divided with number')

   330 

   331     def __nonzero__(self):

   332         return bool(self.sq_m)

   333 

   334 # Shortcuts

   335 D = Distance

   336 A = Area