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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
- from sympy.core.kind import NumberKind
- class BaseScalar(AtomicExpr):
- """
- A coordinate symbol/base scalar.
- Ideally, users should not instantiate this class.
- """
- kind = NumberKind
- 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
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