empty cell array value lost when passed to a function as a part of an anonymous structure

Question

David Goldsmith 2011-7-19

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/11966-empty-cell-array-value-lost-when-passed-to-a-function-as-a-part-of-an-anonymous-structure

采纳的回答： Walter Roberson

在 MATLAB Online 中打开

Consider the following:

>> x % x is a simple two-field structure

x =

    x: 1
    y: 'y'

>> type('printMe.m') % printMe is just a simple function

function printMe(x)
    size(x), x

>> printMe(x)

ans =

1 1

x =

    x: 1
    y: 'y'

>> printMe(struct('x', 1, 'y', 'y')) % Same result passing in an equivalent anonymous struct

ans =

1 1

x =

    x: 1
    y: 'y'

>> % But look what happens if one of the values is an empty cell array

>> printMe(struct('x', 1, 'y', {}))

ans =

0 0

x =

    0x0 struct array with fields:
    x
    y

>> % Is this because it's empty

>> printMe(struct('x', 1, 'y', ''))

ans =

1 1

x =

    x: 1
    y: ''

>> printMe(struct('x', 1, 'y', []))

ans =

1 1

x =

    x: 1
    y: []

>> printMe(struct('x', 1, 'y', struct))

ans =

1 1

x =

    x: 1
    y: [1x1 struct]

>> % Apparently not!

So, apparently, if (and only if) a value in an anonymous struct passed to a function is an empty cell array, the function "loses" all the values in the anonymous struct and thinks it's empty (though, curiously, it doesn't completely "lose" the struct and in particular it retains "knowledge" of its fields, just not the values assigned to those fields).

Bug or "feature," and if the latter, rationale?

Thanks for your time,

OlyDLG