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