Day 18: Operation Order

Classes:

Operation(value)	Represent a mathematical operation.
Tail(op, right)	Represent the tail of an expression.
Node(head, tail)	Represent a node of the abstract syntax tree of a mathematical expression.

Functions:

extract_expression(expr)	Extract the sub-expression surrounded by parentheses in expr.
parse(expression)	Parse the expression into an abstract syntax tree.
serialize(node)	Serialize the abstraction syntax tree given as node to a string.
compute(node)	Evaluate the parsed expression given as node.

class Operation(value)

Represent a mathematical operation.

Attributes:

ADD	Addition
MUL	Multiplication

ADD = '+'

Addition

MUL = '*'

Multiplication

class Tail(op: Operation, right: Union[int, Node])

Represent the tail of an expression.

Attributes:

op	Operation of the mathematical expression
right	Right-hand side of the expression

Methods:

__delattr__(name)	Implement delattr(self, name).
__eq__(other)	Return self==value.
__init__(op, right)
__repr__()	Return repr(self).
__setattr__(name, value)	Implement setattr(self, name, value).

op: Operation

Operation of the mathematical expression

right: Union[int, Node]

Right-hand side of the expression

__delattr__(name)

Implement delattr(self, name).

__eq__(other)

Return self==value.

__init__(op: Operation, right: Union[int, Node]) → None

__repr__()

Return repr(self).

__setattr__(name, value)

Implement setattr(self, name, value).

class Node(head: Union[int, Node], tail: List[Tail])

Represent a node of the abstract syntax tree of a mathematical expression.

Attributes:

head	Constant or left-hand side expression
tail	Remaining expressions on the right-hand side

Methods:

__delattr__(name)	Implement delattr(self, name).
__eq__(other)	Return self==value.
__init__(head, tail)
__repr__()	Return repr(self).
__setattr__(name, value)	Implement setattr(self, name, value).

head: Union[int, Node]

Constant or left-hand side expression

tail: List[Tail]

Remaining expressions on the right-hand side

__delattr__(name)

Implement delattr(self, name).

__eq__(other)

Return self==value.

__init__(head: Union[int, Node], tail: List[Tail]) → None

__repr__()

Return repr(self).

__setattr__(name, value)

Implement setattr(self, name, value).

extract_expression(expr: str) → str

Extract the sub-expression surrounded by parentheses in expr.

Requires

• expr.count("(") == expr.count(")")

• re.match(r"^(.+)", expr)

Ensures

• result in expr

parse(expression: str) → Optional[Node]

Parse the expression into an abstract syntax tree.

serialize(node: Node) → str

Serialize the abstraction syntax tree given as node to a string.

Ensures

• parse(result) == node

compute(node: Node) → int

Evaluate the parsed expression given as node.