make_placeholder_fun: Create a function that creates n placeholders
Description
For internal use by the placeholder_format tweak.
Usage
make_placeholder_fun(pattern)
Arguments
pattern
[character(1)] Any character, optionally followed by 1 or name. Examples: "?", "$1", ":name"
Value
[function(n)] A function with one argument n that
returns a vector of length n with placeholders of the specified format.
Examples: ?, ?, ?, ..., $1, $2, $3, ..., :a, :b, :c