vimrc_reverse_complement

" Put this in your ~/.vimrc
" Define the function to reverse complement a DNA sequence
" Run by calling <Leader>rc from normal mode. By default <Leader> is "\" so press \rc (you only have 1 second after \ to press rc)
function! ReverseComplement()
    " Save the current cursor position
    let save_cursor = getpos('.')

    " Get the word under the cursor
    let word = expand('<cword>')

    " Define a dictionary for DNA base pairs
    let base_pairs = {'A': 'T', 'T': 'A', 'C': 'G', 'G': 'C', 'a': 't', 't': 'a', 'c': 'g', 'g': 'c' }

    " Create a variable for the reverse complement sequence
    let rev_comp_seq = ''

    " Iterate over each character in the word and get its complement
    for i in range(len(word) - 1, -1, -1)
        let char = word[i]
        let rev_comp_seq .= get(base_pairs, char, char)
    endfor

    " Replace only the instance under the cursor with its reverse complement
    execute 's/\%#' . word . '/' . rev_comp_seq . '/g'


    " Restore the cursor position
    call setpos('.', save_cursor)

endfunction

" Map a key sequence to call the ReverseComplement function
nnoremap <Leader>rc :call ReverseComplement()<CR>