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 @property 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'] @property def system(self): return self._system def _sympystr(self, printer): return self._name