function! SwitchToAlternate()
     let l:Filename = expand('%:t:r')
     let l:Extension = expand('%:t:e')
     if l:Extension == "hpp"
         let l:Alternate = l:Filename.".cpp"
         echom "switching to ".l:Alternate
         exec "e ".l:Alternate
     elseif l:Extension == "cpp"
         let l:Alternate = l:Filename.".hpp"
         echom "switching to ".l:Alternate
         exec "e ".l:Alternate
     endif

endfunction

nnoremap <localleader>a :call SwitchToAlternate()<cr>