Use of semicolon in a for loop

Hello,

I think I once read somewhere that using a semicolon in a for loop statement i.e.

for i = 1:N; %With a semicolon
   my_function
end

instead of

for i = 1:N %No semicolon
   my_function
end

was better because the 1:N was not created. However I can't seem to be able to find anything about it anymore. Could someone tell if it's true or not or if not what's the point of using a semicolon?

Answer 1

[Walter Roberson]

"for" does not create the list 1:N in any modern MATLAB (I do not know if it ever did.)

Some people put in semi-colons out of habit, or because they do not realize that they are not needed. Or they might originally have written

for i = 1:N; my_function; end

and reformatted later and forgot to remove the semi-colon.

I do not know if there is any execution or parsing time difference for using the semi-colon. Some MATLAB versions have had timing oddities so I would not rule out the possibility.

[Daniel Shub]

You beat me ...

Answer 2

[Daniel Shub]

I don't think a semicolon or comma adds anything. It does allow everything to be written on one line like

   for i = 1:N; my_function, end

Outside of the command window, I am not sure why you would want to do this.

[Walter Roberson]

All on one line like that can have notably different timing than each on separate lines, at least prior to 2010b (I think it was.) Slower on one line, I think it was.

[Daniel Shub]

I also believe it is slower. I am pretty sure if it was faster, my code would look a lot different. Imagine how unreadable code would be if it all had to be on one line.

[Côme]

You don't even need it inside the command window.

[Daniel Shub]

No, you don't need it, but sometimes it is easier. I find tab completion and the history behaves better if it is all on one line.