Vim option for automatically inserting ">" at start of line

Question

Suppose I have a file test.c containing the following:

// line 1
// line 2

If I open this file in Vim and navigate to the first line in normal mode, then type o, I get the following:

// line 1
// 
// line 2

Now suppose I have a file test.lhs (literate Haskell) containing

> data X = A | B
> data Y = C | D

If I open this file and navigate to the first line in normal mode, then type o, I get

> data X = A | B

> data Y = C | D

Question: How can I make Vim automatically insert > at the start of the line for the .lhs file, similar to how // is automatically inserted for the .c file?

Answer 1

Got it! To .vimrc, add

set formatoptions+=o

This automatically inserts the "comment leader" (character sequence indicating a comment, or, in the case of literate Haskell, the Haskell code) at the start of the line.

For more information on the options accepted by formatoptions, type :help fo-table.