I don't know what exactly you mean by pasting a function around the selection, but you can paste selections, registers or even files at specific lines with some vim-fu. If it's generic enough you could write a function or even a keyboard shortcut if it's very simple.

I have set ",',(,[,{ in visual mode to cut the selection insert the pairs then paste it back as a very hacky solution, but it gets the job done. If you want something more advanced to add or change anything around the selection tpope has solved that with vim-surround[1].

[1]: https://github.com/tpope/vim-surround