nd2py.core.tree package

Submodules

nd2py.core.tree.iter_postorder module

class nd2py.core.tree.iter_postorder.IterPostorder

Bases: IterPreorder

Post-order iteration over a tree structure. Yields each node before its children.

generic_visit(node: Symbol, *args, **kwargs)

nd2py.core.tree.iter_preorder module

class nd2py.core.tree.iter_preorder.IterPreorder

Bases: Visitor

Pre-order iteration over a tree structure. Yields each node before its children.

is_yielded_node(yielded)

generic_visit(node: Symbol, *args, **kwargs)

nd2py.core.tree.match module

nd2py.core.tree.tree_mixin module

class nd2py.core.tree.tree_mixin.TreeMixin

Bases: object

Mixin 类：负责维护 Symbol 作为一棵符号树的结构关系 (parent, operands) 并提供树形操作方法。 宿主类必须提供以下属性:

• self.n_operands

• self.parent

• self.operands

n_operands: int

parent: 'Symbol' | None

operands: List['Symbol']

property root

iter_preorder()

Non-recursive preorder traversal of the Symbol tree using an explicit stack.

iter_postorder()

Postorder traversal of the Symbol tree.

replace(child: Symbol, other: Symbol, no_warn=False)

Replace current expression (or subexpression denoted by child) with another expression.

path_to(child: Symbol) → str

Get the path from self to child.

get_path(path: Tuple[int]) → Symbol

Get the subexpression at the specified path.

match(pattern: Symbol) → Dict[str, Symbol] | None

Match a pattern expression against self expression.

This function checks if the pattern can match the self expression by comparing their tree structures. Variables in the pattern can match any subexpression. The same variable name must match the same subexpression throughout the pattern.

Parameters:

pattern – The pattern expression containing variables to be matched.

Returns:

A dictionary mapping variable names from the pattern to their matched subexpressions, or None if the pattern does not match.

Examples

>>> from nd2py import Variable, sin, Add, Mul
>>> from nd2py.core.tree import match
>>> a = Variable('a')
>>> x = Variable('x')

>>> # sin(a) matches sin(x*2+1)
>>> f = sin(x*2+1)
>>> f.match(sin(a))
{'a': x + 2*x}

>>> # a+a matches sin(x)+sin(x) (same variable must match same subexpression)
>>> f = sin(x) + sin(x)
>>> f.match(a+a)
{'a': sin(x)}

>>> # a+a does NOT match sin(x)+cos(x) (different subexpressions)
>>> f = sin(x) + cos(x)
>>> f.match(a+a)
None

>>> # a+b matches both sin(x)+sin(x) and sin(x)+cos(x)
>>> f = sin(x) + sin(x)
>>> f.match(a+b)
{'a': sin(x), 'b': sin(x)}