Error: Missing subscript
Why does the error actually mean in the code:
But there's no error for this code:
Whats the technical difference?
void mat(int matrix[][]);But there's no error for this code:
void mat(int matrix[]);Whats the technical difference?
int matrix[] is an incomplete type when used as a paramter. Use int* matrix instead.
int matrix[][] is meaningless. Use int** matrix instead.
Please note that the array sizes are not passed, you must pass these seperately.
There's some background here: http://www.cplusplus.com/forum/general/70081/#msg373940
int matrix[][] is meaningless. Use int** matrix instead.
Please note that the array sizes are not passed, you must pass these seperately.
There's some background here: http://www.cplusplus.com/forum/general/70081/#msg373940
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To quote the C standard:
6.2.5.22 goes on to say:
What does that mean?
It means that for:
the size is not needed. It can be treated as an array of int of unspecified size where the size isn't needed. Incrementing a pointer to the next element of the array means adding sizeof(int) to the pointer.
For:
a 2D array (an array of int[]) is specified, but we don't know the size of int[]. In this case, the size is needed. We don't know how to increment the pointer to an int[].
For:
a 2D array (an array of int[1]) is specified. We know how to increment the pointer to the next element, it's sizeof(int) * 1.
Why all this? The background link I posted earlier talks about the history of the treatment of arrays.
| An incomplete type may only by used when the size of an object of that type is not needed. It is not needed, for example, when a typedef name is declared to be a specifier for a structure or union, or when a pointer to or a function returning a structure or union is being declared. (See incomplete types in 6.2.5.) The specification has to be complete before such a function is called or defined. |
6.2.5.22 goes on to say:
| An array type of unknown size is an incomplete type. It is completed, for an identifier of that type, by specifying the size in a later declaration (with internal or external linkage). |
What does that mean?
It means that for:
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For:
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For:
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Why all this? The background link I posted earlier talks about the history of the treatment of arrays.
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Did you read the link I posted earlier?
And why would you try to pass a
And why would you try to pass a
matrix[5][5] to a void mat(int matrix[][1])? Hopefully you'll get a type mismatch error.
And is there any difference in these two statements?
void mat(int mat[]);void mat(int mat[20]);
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