Return NotImplemented for Expr and GenExpr operators to simplify

[Zeroto521]

Python prefers to use NotImplemented to handle the unknown input types. It's clear.

Here is an example.
A.__add__ can only receive int type. But a + b can work. When Python calls A.__add__(B), it returns NotImplemented. Then Python will call B.__radd__(A). If both of them are NotImplemented, Python will raise a TypeError.

So we use NotImplemented to simplify Expr, GenExpr, and MatrixExpr.

from __future__ import annotations


class A:
    def __init__(self, value: int):
        self.value = value

    def __add__(self, other: int) -> int:
        if not isinstance(other, int):
            return NotImplemented
        return self.value + other


class B:
    def __init__(self, value: int):
        self.value = value

    def __add__(self, other: A) -> B:
        if not isinstance(other, A):
            return NotImplemented
        return self.value + other.value

    def __radd__(self, other: A) -> int:
        if not isinstance(other, A):
            return NotImplemented
        return self.value + other.value


if __name__ == "__main__":
    a = A(5)
    b = B(10)

    print(a + 3)  # print 8
    print(a + b)  # print 15
    print(a + "test")  # raises TypeError
# Traceback (most recent call last):
#   File "test.py", line 35, in <module>
#     print(a + "test")  # raises TypeError
#           ~~^~~~~~~~
# TypeError: unsupported operand type(s) for +: 'A' and 'str'

[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 5 comments.

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[Joao-Dionisio]

After addressing Copilot's comments, this can be merged.

[Joao-Dionisio]

@Zeroto521 can you please resolve the conflicts so I merge this?

[Zeroto521]

@Zeroto521 can you please resolve the conflicts so I merge this?

@Joao-Dionisio, it will raise an error if I merge the master branch directly first. See details here: #1182 (comment)

[Joao-Dionisio]

#1203 has been merged.

[Zeroto521]

Should this PR be in 6.2.0 or an unreleased version?