Matlab：“使用assignin错误：尝试添加”c“到静态工作空间“ [英] Matlab: "Error using assignin: Attempt to add "c" to a static workspace"

问题描述

我有以下功能定义（测试代码）：

I have the following piece of function definition (test code):

function [X,Y,Z] = test(x,y,z)

syms a b c;
a = b + c;   % This is where it gets wrong

X=x;
Y=y;
Z=z;

keyboard

% nested functions
    function y = fun1(t,x)
        y=t+x;
    end

    function res = bvpbc(y0,yT)
       res= y0+yT;
    end

end

基本上，我有一些嵌套函数在测试函数中，我声明了一些符号变量 a ， b 和 c 。但是，当我通过输入

Basically, I have some nested functions within the test function, where I declared some symbolic variables a, b and c. However, when I run the function by typing

test（1,1,1）

总是有这个错误消息：

Error using assignin
Attempt to add "b" to a static workspace.
 See MATLAB Programming, Restrictions on Assigning to
 Variables for details.

Error in syms (line 66)
        assignin('caller',x,sym(x));

Error in test (line 3)
    syms a b c;

这似乎是符号声明有问题，但我不明白为什么。如何解决？

It seems to be something wrong with the symbolic declarations, but I don't understand why. How can I fix it?

谢谢！

编辑：另外每当我删除两个嵌套函数时，测试函数将正常工作。

In addition, whenever I remove the two nested functions, the test function will work just fine.

推荐答案

以下最小工作示例重新创建了问题，并且作为 Andrew Janke 在评论中解释，不是一个错误：

The following minimal working example recreates the problem, and as Andrew Janke explains in the comments, is not a bug:

function foo
syms A

    function nested
    end

end

您可以通过将符号变量的工作区显式分配给工作区来解决问题：

you can work around it with an explicit assignment of the symbolic variable to the workspace:

A = sym('A');

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