如何在 sympy 1.3 上进行区间算术? [英] How to do interval arithmetic on sympy 1.3?

问题描述

我如何在 Sympy 1.3 中进行区间运算?(特别是加法和乘法)

How do I do interval arithmetic in Sympy 1.3? (specifically, addition and multiplication)

例如，给定:

q1 = Interval(0,255)
q2 = Interval(0,255)

这两个区间的相加应该是Interval(0, 510).(加号运算符被重载为联合"，因此 q1+q2 产生 Interval(0,255).)

The addition of those two intervals should be Interval(0, 510). (The plus operator is overloaded to mean "union", so q1+q2 yields Interval(0,255).)

如果我尝试 Add(q1, q2)，我会得到一个异常:

If I try Add(q1, q2), I get an exception:

  Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python2.7/dist-packages/sympy/core/cache.py", line 93, in wrapper
    retval = cfunc(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/sympy/core/compatibility.py", line 850, in wrapper
    result = user_function(*args, **kwds)
  File "/usr/local/lib/python2.7/dist-packages/sympy/core/operations.py", line 45, in __new__
    c_part, nc_part, order_symbols = cls.flatten(args)
  File "/usr/local/lib/python2.7/dist-packages/sympy/core/add.py", line 223, in flatten
    newseq.append(Mul(c, s))
  File "/usr/local/lib/python2.7/dist-packages/sympy/core/cache.py", line 93, in wrapper
    retval = cfunc(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/sympy/core/compatibility.py", line 850, in wrapper
    result = user_function(*args, **kwds)
  File "/usr/local/lib/python2.7/dist-packages/sympy/core/operations.py", line 45, in __new__
    c_part, nc_part, order_symbols = cls.flatten(args)
  File "/usr/local/lib/python2.7/dist-packages/sympy/core/mul.py", line 186, in flatten
    r, b = b.as_coeff_Mul()
AttributeError: 'Interval' object has no attribute 'as_coeff_Mul'

(Mul 也有类似的异常).

(I get a similar exception for Mul).

然而，添加两个间隔的代码似乎就在这里:https://github.com/sympy/sympy/blob/sympy-1.3/sympy/sets/handlers/add.py#L22

Yet, the code to add two intervals seems to be right here: https://github.com/sympy/sympy/blob/sympy-1.3/sympy/sets/handlers/add.py#L22

但是调度器机制似乎没有捕捉到 Interval + Interval 的情况.

But the dispatcher mechanism doesn't seem to be catching the case of Interval + Interval.

如何在 sympy 中对间隔进行加法和乘法?

How do I do addition and multiplication on intervals in sympy?

推荐答案

Sympy Intervals 不执行区间算术.您在存储库中找到的函数是 sympy.sets.setexpr.SetExpr 的处理程序之一，这是一种采用给定集合中的值的表达式类型:

Sympy Intervals do not perform interval arithmetic. The function you found in the repository is one of the handlers for sympy.sets.setexpr.SetExpr, an expression type that takes values in a given set:

from sympy import Interval
from sympy.sets.setexpr import SetExpr

q1 = SetExpr(Interval(0, 255))
q2 = SetExpr(Interval(0, 255))

result = q1 + q2

SetExpr 目前是隐藏的，而且大部分都没有记录.

SetExpr is currently hidden-ish and mostly undocumented.

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