"""Tools for defining lineshapes with `sympy`."""
import functools
from abc import abstractmethod
from typing import Any, Callable, Type
import sympy as sp
from sympy.printing.latex import LatexPrinter
[docs]class UnevaluatedExpression(sp.Expr):
"""Base class for classes that expressions with an ``evaluate()`` method.
Derive from this class when decorating a class with :func:`implement_expr`
or :func:`implement_doit_method`. It is important to derive from
`UnevaluatedExpression`, because an :code:`evaluate()` method has to be
implemented.
"""
@abstractmethod
def evaluate(self) -> sp.Expr:
pass
@abstractmethod
def _latex(self, printer: LatexPrinter, *args: Any) -> str:
"""Provide a mathematical Latex representation for notebooks."""
args = tuple(map(printer._print, self.args))
return f"{self.__class__.__name__}{args}"
[docs]def implement_expr(
n_args: int,
) -> Callable[[Type[UnevaluatedExpression]], Type[UnevaluatedExpression]]:
"""Decorator for classes that derive from `UnevaluatedExpression`.
Implement a `~object.__new__` and `~sympy.core.basic.Basic.doit` method for
a class that derives from `~sympy.core.expr.Expr` (via
`UnevaluatedExpression`).
"""
def decorator(
decorated_class: Type[UnevaluatedExpression],
) -> Type[UnevaluatedExpression]:
decorated_class = implement_new_method(n_args)(decorated_class)
decorated_class = implement_doit_method()(decorated_class)
return decorated_class
return decorator
[docs]def implement_new_method(
n_args: int,
) -> Callable[[Type[UnevaluatedExpression]], Type[UnevaluatedExpression]]:
"""Implement ``__new__()`` method for an `UnevaluatedExpression` class.
Implement a `~object.__new__` method for a class that derives from
`~sympy.core.expr.Expr` (via `UnevaluatedExpression`).
"""
def decorator(
decorated_class: Type[UnevaluatedExpression],
) -> Type[UnevaluatedExpression]:
def new_method(
cls: Type,
*args: sp.Symbol,
**hints: Any,
) -> bool:
if len(args) != n_args:
raise ValueError(
f"{n_args} parameters expected, got {len(args)}"
)
args = sp.sympify(args)
evaluate = hints.get("evaluate", False)
if evaluate:
return sp.Expr.__new__(cls, *args).evaluate() # type: ignore # pylint: disable=no-member
return sp.Expr.__new__(cls, *args)
decorated_class.__new__ = new_method # type: ignore
return decorated_class
return decorator
[docs]def implement_doit_method() -> Callable[
[Type[UnevaluatedExpression]], Type[UnevaluatedExpression]
]:
"""Implement ``doit()`` method for an `UnevaluatedExpression` class.
Implement a `~sympy.core.basic.Basic.doit` method for a class that derives
from `~sympy.core.expr.Expr` (via `UnevaluatedExpression`).
"""
def decorator(
decorated_class: Type[UnevaluatedExpression],
) -> Type[UnevaluatedExpression]:
@functools.wraps(decorated_class.doit)
def doit_method(self: Any, deep: bool = True, **hints: Any) -> sp.Expr:
expr = type(self)(*self.args, **hints, evaluate=True)
if deep:
return expr.doit()
return expr
decorated_class.doit = doit_method
return decorated_class
return decorator
[docs]def create_expression(
cls: Type[UnevaluatedExpression],
*args: Any,
evaluate: bool = False,
**kwargs: Any,
) -> sp.Expr:
"""Helper function for implementing :code:`Expr.__new__`.
See e.g. source code of `.BlattWeisskopfSquared`.
"""
args = sp.sympify(args)
expr = sp.Expr.__new__(cls, *args, **kwargs)
if evaluate:
return expr.evaluate() # pylint: disable=no-member
return expr