How to modify an array in function?

MATLAB is a pass by value language. I have a recursive function that processes pixel's neighbors. It is very expensive to make the copy of the image (in my case two images) each time the function is called.

I used global variables to solve the problem. Is there any other way to make a recursive function modify an array?

---

You have three options here, but maybe you don't need any of them, since Matlab used 'copy-on-write', ie variables are only copied if you modify them.

As @gnovice mentions, you can use a nested function. Variables used inside the nested function are shared between the nested function and the enclosing function. Nested functions are somewhat tricky to debug, and a bit more complicated to write/understand.

You can store your images as properties of a handle object, which is passed by reference.

You can write code differently in order to not use a recursive function, since Matlab isn't the best language for using those. If you have access to the image processing toolbox, you may be able to use functions like blockproc , or im2col to rewrite the function.

Finally, if you want to stay with your current scheme, I strongly suggest using persistent variables instead of globals.

---

MATLAB is not always pass-by-value, newer versions of MATLAB do pass-by-reference under some circumstances, see in-place operations and a more general discussion about MATLAB memory management in this SO post.

Without tail-call optimization it is inefficient to use recursion and MATLAB does not have it as far I know, but every recursion can be transformed into a loop.

---

如果将递归函数作为存储图像数据的另一个函数中的嵌套函数，则递归函数可以修改图像数据而无需传递给它。

链接地址: http://www.djcxy.com/p/80512.html

上一篇: ES6尾递归优化堆栈溢出

下一篇: 如何修改函数中的数组？