What is the data type of the output of the length function?

Why not indicated in the description? http://www.mathworks.com/help/matlab/ref/length.html

I guess it is double, but why? Length is always an integer value!

Answer 1

[Guillaume]

The default data type in matlab is double, not integer as in most compiled languages. array lengths, array indices, etc. are all stored as double.

Note that all integers up to flintmax (~9e15) can be accurately stored as double so it's not an issue at the moment. It'll be a while before computers have enough memory for it to become a problem.

Answer 2

[Azzi Abdelmalek]

length(A) is always integer value, but the greatest integer value, is uint64(2^64-1). The length of an array could be greater then this value

[Guillaume]

"The length of an array could be greater then this value"

Hardly, even if the array took only one byte per elements, you're in the exabyte realm. You won't find a computer with that kind of storage (and I doubt matlab could cope with it anyway).

[Azzi Abdelmalek]

You are right, I didn't realize that the number 2^64 is too big!