Support repeat/logic control for `newcommand` extension

I want to simulate some commands which supported by amsmath package, but without logic control, it won't be possible, so I wonder is there any way to do this, or will you add this feature?

Syntax might like this:

\newcommand\hdotsfor[1]{%
  \foreach \index in {1, ..., #1} {%
   \ifnum\index!=1{$}  \cdots %
  }}

Invoke \hdotsfor{3} will get: $$ \cdots & \cdots & \cdots $$