Two ways of M-subfunction definition: what are discrepances?

2011 5 18
3 个回答
回答已采纳
5 次查看（30 天）

2 个投票

As known, there are 2 ways -- nested subroutines and secondaries subr.
1. nested
function...
...
function...
...
end
...
end
2. primary/secondary
function
...
end
function
...
end
From header (primary function)one can call both nested and secondary subfunctions.
But what kind is better to use? What are differences between ?

请先登录，再回答此问题。

 采纳的回答

Andrew Newell
Andrew Newell 2011-5-18

1 个投票

The primary/secondary functions are much like two functions in separate files, except that the secondary functions (called subfunctions) are only seen by the other functions in the same file. Generally, the variables in functions should be hidden from each other, so this is the default choice. Use nested functions when you need the specific advantages that stem from having access to variables in the workspace of the calling function.
Nested functions are great for:
  1. "Memoizing" (storing) results of costly calculations for later use (see Loren's blog).
  2. Creating custom functions with hidden parameters that are set by the calling function (as in this example). This is like a fancy anonymous function.

1 个评论
显示 -1更早的评论 隐藏 -1更早的评论

Matt Fig
Matt Fig 2011-5-18
I would add
3. GUI callbacks. The use of nested functions for GUIs eliminates almost all "How do I share data between callbacks" questions. When I write a complex GUI, it is only with nested functions anymore.

请先登录，再进行评论。

更多回答（2 个）

Yoav Livneh
Yoav Livneh 2011-5-18

2 个投票

In the first case, the second function is nested and only the outer function can call it. Furthermore the nested function can read and use parameters from the caller function's workspace.
In the second case each function has its own workspace and they don't share parameters.
Igor
Igor 2011-5-18

0 个投票

Thanks for answers. As I understand, if varname in nested func. coincides with varname in primary func. that uses variable that was defined in primary func. Perhaps, secondary func. is like private methods in object oriented programming.
Another question, on analogy with C++. When I call nested or secondary func. -- subfun(par) -- a new region of memory is reserved and here value is copied from calling func. That is -- dublicating exists.

2 个评论
显示 无 隐藏 无

Andrew Newell
Andrew Newell 2011-5-18
Yes, subfunctions are a bit like private methods.
No, the value of a function argument is not copied unless the argument is changed within the function. See http://www.mathworks.com/help/techdoc/matlab_prog/brh72ex-2.html#brh72ex-13.
Igor
Igor 2011-5-18
On 2nd question: but if changed then copied!
Very rational rule!

请先登录，再进行评论。

类别

在 帮助中心 和 File Exchange 中查找有关 Programming 的更多信息

产品

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by