How to let a register contain exactly one ^M without an extra newline?

Question

I'm trying to programmatically record a macro (using :let @m= rather than qm). In vim, I executed:

:let @m = ':retab^M'

where ^M is typed as ctrl+V, Enter. I expect the buffer to contain exactly what is written above, but it also contains a newline at the end, and when the macro is executed, my cursor moves down by one line. If I populate @m with the q record function, this problem does not occur.

How can I programmatically set a register to contain a ^M but not an extra newline? Note that :let @m=":retab\<cr>" gives the same result.

To elaborate: I expect the @m to contain ':retab^M' or ':retab\n' but it actually contains: ':retab\n\n' with an extra newline. Or to say it another way, :let @m = ':retab^M' and qm:retab ENTER q should give the same result (the identical macro in register m), but they differ by a newline character. (The result is the same on Windows and Linux.)

Answer 1

Could you try to replace c-m to c-j?

like

let @m = ':retab^@'

Not 100% sure why it happens but...

When you do (with <C-v><C-m>)

let @m = ':retab^M'

The m register gets additional 'newline' and looks like:

:retab^M^@

But if instead of ^M you will insert ^@, no additional 'newline' is inserted and you end up with:

:retab^@

PS

to see contents of the register use:

echomsg @m

echo @m will not show those special symbols.

Answer 2

You could use the following, if you don't want to <C-V>...:

let @m=":retab\n"

Note: You need double-quotes. Doesn't work with single quotes.