Where is documentation for colon range of the form 1:vector?

I think the following code examples should result in a Matlab error and not be allowed to run. I think the code syntax should be disallowed by Matlab.

Where is the documentation that describes the use of the colon operator having the following form? All the examples in https://www.mathworks.com/help/matlab/ref/colon.html appear to use only scalar integers.

I was reviewing code that had code analogous to:

a = [ 3 9 44];
b = 1:a

b = 1×3

1 2 3

I didn't recognize this form. The results appear to show that only the first element of a is used. Where is the documentation that allows this?

A quick experiment shows that the first element sof both vectors are used when creating a range:

a = [2 12 11];
b = [ 13 19 144];
c = a:b

c = 1×12

2 3 4 5 6 7 8 9 10 11 12 13

Answer 1

[Steven Lord]

The third item in the Description section of the documentation page to which you link describes what the colon, : operator does when its inputs are non-scalar.

"x = j:i:k creates a regularly-spaced vector x using i as the increment between elements. The vector elements are roughly equal to [j,j+i,j+2*i,...,j+m*i] where m = fix((k-j)/i). However, if i is not an integer, then floating point arithmetic plays a role in determining whether colon includes the endpoint k in the vector, since k might not be exactly equal to j+m*i. If you specify nonscalar arrays, then MATLAB interprets j:i:k as j(1):i(1):k(1)." [Emphasis added.]

[Paul Hoffrichter]

OK, thanks. I think nonscalar arrays in this context should be an error. In this case, the author was surprised that the imported code was written that way.

[Steven Lord]

I've forwarded this feedback to the appropriate developers.

[Paul Hoffrichter]

Thanks @Steven Lord

[Stephen23]

This should definitely be deprecated. And also that counter-productive column-iteration behavior of FOR.