Is there a way to set an option to the value of another option?

Question

For example, I'd like to set

set tabstop=4
set shiftwidth=4

Is there a way to do something like

set tabstop=4
set shiftwidth=tabstop

so I can set both values by only changing a single number?

Answer 1

You can use the let command instead.

Like so:

let &shiftwidth = &tabstop

The & specifies that the variable name is a Vim option. You can also do :help let-option to know more about it:

:let &{option-name} = {expr1}
        Set option {option-name} to the result of the
        expression {expr1}.  A String or Number value is
        always converted to the type of the option.
        For an option local to a window or buffer the effect
        is just like using the |:set| command: both the local
        value and the global value are changed.

Answer 2

Might be a better way but you could always do this:

exec 'set shiftwidth=' . &tabstop

Answer 3

Specifically in this case:

http://vimhelp.appspot.com/options.txt.html#%27softtabstop%27:

When 'sts' is negative, the value of 'shiftwidth' is used.

http://vimhelp.appspot.com/options.txt.html#%27shiftwidth%27

When ['shiftwidth' is] zero the 'ts' value will be used.