Having some problems with recursive function

Question

David Joseph 2019-4-5

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/454616-having-some-problems-with-recursive-function

评论： David Joseph 2019-4-6

function S = mySum(A)
S = plus(A, length(A))
function total = plus(arr, leng)
if(leng == 0)
   total = 0
else
   total = arr(leng) + plus(arr,leng - 1)
end

The above codes is used for computing the sum of the elements in an array. The problem here is that the function always returns "total = 0".

However, the function returns the correct value if i change

total = arr(leng) + plus(arr,leng - 1)

to

total = arr(leng) () plus(arr,leng - 1)

After debugging the script several times i realized some strange behaviours at "total". After plus(arr, 0) return 'total = 0'.

It will be total = arr(1) + 0, so this should be the sum of arr(1) and '0'. However, this calls plus(arr(1), 0).

Therefore, when i change :

if(leng == 0)

total = 50

Again, 'total = arr(leng) + plus(arr, leng - 1)' calls function plus(arr(leng), plus(arr, leng - 1)).

Here, 'total = arr(1) + plus(arr, 0)' calls function plus(arr(1), 50).

Can someone please explain whether 'total = arr(leng) + plus(arr,leng - 1)' calls (arr(leng), plus(arr, leng - 1)) or not and also the solution in this case.

Thanks a lot for your contribution.

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Answer 1

Dennis 2019-4-5

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/454616-having-some-problems-with-recursive-function#answer_369206

编辑：Dennis 2019-4-5

在 MATLAB Online 中打开

This strange behaviour originates in a unfortunate function name.

function S = mySum(A)
S = myplus(A, length(A))
function total = myplus(arr, leng)
if(leng == 0)
   total = 0
else
   total = arr(leng) + myplus(arr,leng - 1)
end