matlab - Difference between accessing cell elements using curly braces and parentheses

Question

What is the difference between accessing elements in a cell array using parentheses () and curly braces {}?

For example, I tried to use cell{4} = [] and cell(4) = []. In the first case it sets the 4^th element to [], but in the second case it wiped out the cell element, that is, reduced the cell element count by 1.

Answer 1

Think of cell array as a regular homogenic array, whose elements are all cells. Parentheses (()) simply access the cell wrapper object, while accessing elements using curly bracers ({}) gives the actual object contained within the cell.

For example,

A={ [5,6], 0 , 0 ,0 };

Will look like this:

The syntax of making an element equal to [] with parentheses is actually a request to delete that element, so when you ask to do foo(i) = [] you remove the i-th cell. It is not an assignment operation, but rather a RemoveElement operation, which uses similar syntax to assignment.

However, when you do foo{i} = [] you are assigning to the i-th cell a new value (which is an empty array), thus clearing the contents of that cell.