Function line_span::find_prev_line_start

pub fn find_prev_line_start(text: &str, index: usize) -> Option<usize>

Find the start (byte index) of the previous line, the line before the one which index is within.

Returns None if there is no previous line.

See also

• find_prev_line_range to find both start and end of the previous line.
• find_prev_line_end to find the end of the previous line.
• find_line_start to find the start of the current line.
• find_next_line_start to find the start of the next line.

Panics

Panics if index is out of bounds.

Example

let text = "foo\nbar\nbaz";
let i = 9; // 'a'

let start = line_span::find_prev_line_start(text, i).unwrap();

assert_eq!(start, 4);
assert_eq!(&text[start..], "bar\nbaz");