72 lines
2.0 KiB
Python
72 lines
2.0 KiB
Python
from sympy.core import AtomicExpr, Symbol, S
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from sympy.core.sympify import _sympify
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from sympy.printing.pretty.stringpict import prettyForm
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from sympy.printing.precedence import PRECEDENCE
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class BaseScalar(AtomicExpr):
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"""
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A coordinate symbol/base scalar.
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Ideally, users should not instantiate this class.
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Unicode pretty forms in Python 2 should use the `u` prefix.
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"""
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def __new__(cls, index, system, pretty_str=None, latex_str=None):
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from sympy.vector.coordsysrect import CoordSys3D
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if pretty_str is None:
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pretty_str = "x{}".format(index)
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elif isinstance(pretty_str, Symbol):
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pretty_str = pretty_str.name
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if latex_str is None:
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latex_str = "x_{}".format(index)
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elif isinstance(latex_str, Symbol):
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latex_str = latex_str.name
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index = _sympify(index)
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system = _sympify(system)
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obj = super().__new__(cls, index, system)
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if not isinstance(system, CoordSys3D):
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raise TypeError("system should be a CoordSys3D")
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if index not in range(0, 3):
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raise ValueError("Invalid index specified.")
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# The _id is used for equating purposes, and for hashing
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obj._id = (index, system)
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obj._name = obj.name = system._name + '.' + system._variable_names[index]
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obj._pretty_form = '' + pretty_str
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obj._latex_form = latex_str
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obj._system = system
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return obj
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is_commutative = True
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is_symbol = True
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@property
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def free_symbols(self):
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return {self}
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_diff_wrt = True
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def _eval_derivative(self, s):
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if self == s:
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return S.One
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return S.Zero
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def _latex(self, printer=None):
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return self._latex_form
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def _pretty(self, printer=None):
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return prettyForm(self._pretty_form)
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precedence = PRECEDENCE['Atom']
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@property
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def system(self):
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return self._system
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def _sympystr(self, printer):
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return self._name
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