is it possible to provide an optional arg in cmd?

[superiums]

is it possible to provide an optional arg in cmd?
e.g. i have the following cmd, in which the arg $1 was optional:

cmd paste-to %{{
   if [[ -n "$1" ]]; then
     cp -r --backup=numbered -i -- $fx $1
     [[ -d "$1" ]] \
       && lf -remote "send $id :unselect; cd $1;" \
       || lf -remote "send $id :unselect; select $1; " 
   else
     echo "Cancelled."
   fi
}}
map pt push :paste-to<space>

but it report an error while arg $1 was not provided:

---: line 3: $1: unbounded varable

[joelim-work]

Shell commands (starting with $/!/%/&) are evaluated using a shell, so you should be able to use ${1:-foo}.

[superiums]

Thanks very much.