Fast word count function in Vim

Question

I am trying to display a live word count in the vim statusline. I do this by setting my status line in my .vimrc and inserting a function into it. The idea of this function is to return the number of words in the current buffer. This number is then displayed on the status line. This should work nicely as the statusline is updated at just about every possible opportunity so the count will always remain 'live'.

The problem is that the function I have currently defined is slow and so vim is obviously sluggish when it is used for all but the smallest files; due to this function being executed so frequently.

In summary, does anyone have a clever trick for producing a function that is blazingly fast at calculating the number of words in the current buffer and returning the result?

Answer 1

Keep a count for the current line and a separate count for the rest of the buffer. As you type (or delete) words on the current line, update only that count, but display the sum of the current line count and the rest of the buffer count.

When you change lines, add the current line count to the buffer count, count the words in the current line and a) set the current line count and b) subtract it from the buffer count.

It would also be wise to recount the buffer periodically (note that you don't have to count the whole buffer at once, since you know where editing is occurring).

Answer 2

So I've written:

func CountWords()
    exe "normal g\"
    let words = substitute(v:statusmsg, "^.*Word [^ ]* of ", "", "")
    let words = substitute(words, ";.*", "", "")
    return words
endfunc

But it prints out info to the statusbar, so I don't think it will be suitable for your use-case. It's very fast, though!

Answer 3

This will recalculate the number of words whenever you stop typing for a while (specifically, updatetime ms).

let g:word_count="<unknown>"
fun! WordCount()
    return g:word_count
endfun
fun! UpdateWordCount()
    let s = system("wc -w ".expand("%p"))
    let parts = split(s, ' ')
    if len(parts) > 1
        let g:word_count = parts[0]
    endif
endfun

augroup WordCounter
    au! CursorHold * call UpdateWordCount()
    au! CursorHoldI * call UpdateWordCount()
augroup END

" how eager are you? (default is 4000 ms)
set updatetime=500

" modify as you please...
set statusline=%{WordCount()}\ words

Enjoy!

Answer 4

Using the method in the answer provided by Steve Moyer I was able to produce the following solution. It is a rather inelegant hack I'm afraid and I feel that there must be a neater solution, but it works, and is much faster than simply counting all of the words in a buffer every time the status line is updated. I should note also that this solution is platform independent and does not assume a system has 'wc' or something similar.

My solution does not periodically update the buffer, but the answer provided by Mikael Jansson would be able to provide this functionality. I have not, as of yet, found an instance where my solution becomes out of sync. However I have only tested this briefly as an accurate live word count is not essential to my needs. The pattern I use for matching words is also simple and is intended for simple text documents. If anyone has a better idea for a pattern or any other suggestions please feel free to post an answer or edit this post.

My solution:

"returns the count of how many words are in the entire file excluding the current line 
"updates the buffer variable Global_Word_Count to reflect this
fu! OtherLineWordCount() 
    let data = []
    "get lines above and below current line unless current line is first or last
    if line(".") > 1
     let data = getline(1, line(".")-1)
    endif 
    if line(".") < line("$")
     let data = data + getline(line(".")+1, "$") 
    endif 
    let count_words = 0
    let pattern = "\\<\\(\\w\\|-\\|'\\)\\+\\>"
    for str in data
     let count_words = count_words + NumPatternsInString(str, pattern)
    endfor 
    let b:Global_Word_Count = count_words
    return count_words
endf    

"returns the word count for the current line
"updates the buffer variable Current_Line_Number 
"updates the buffer variable Current_Line_Word_Count 
fu! CurrentLineWordCount()
    if b:Current_Line_Number != line(".") "if the line number has changed then add old count
     let b:Global_Word_Count = b:Global_Word_Count + b:Current_Line_Word_Count
    endif 
    "calculate number of words on current line
    let line = getline(".")
    let pattern = "\\<\\(\\w\\|-\\|'\\)\\+\\>"
    let count_words = NumPatternsInString(line, pattern)
    let b:Current_Line_Word_Count = count_words "update buffer variable with current line count
    if b:Current_Line_Number != line(".") "if the line number has changed then subtract current line count
     let b:Global_Word_Count = b:Global_Word_Count - b:Current_Line_Word_Count
    endif 
    let b:Current_Line_Number = line(".") "update buffer variable with current line number
    return count_words
endf    

"returns the word count for the entire file using variables defined in other procedures
"this is the function that is called repeatedly and controls the other word
"count functions.
fu! WordCount()
    if exists("b:Global_Word_Count") == 0 
     let b:Global_Word_Count = 0
     let b:Current_Line_Word_Count = 0
     let b:Current_Line_Number = line(".")
     call OtherLineWordCount()
    endif 
    call CurrentLineWordCount()
    return b:Global_Word_Count + b:Current_Line_Word_Count
endf

"returns the number of patterns found in a string 
fu! NumPatternsInString(str, pat)
    let i = 0
    let num = -1
    while i != -1
     let num = num + 1
     let i = matchend(a:str, a:pat, i)
    endwhile
    return num
endf

This is then added to the status line by:

:set statusline=wc:%{WordCount()}

I hope this helps anyone looking for a live word count in Vim. Albeit one that isn't always exact. Alternatively of course g ctrl-g will provide you with Vim's word count!

Answer 5

Here's a usable version of Rodrigo Queiro's idea. It doesn't change the status bar, and it restores the statusmsg variable.

function WordCount()
  let s:old_status = v:statusmsg
  exe "silent normal g\<c-g>"
  let s:word_count = str2nr(split(v:statusmsg)[11])
  let v:statusmsg = s:old_status
  return s:word_count
endfunction

This seems to be fast enough to include directly in the status line, e.g.:

:set statusline=wc:%{WordCount()}

Answer 6

I took the bulk of this from the vim help pages on writing functions.

function! WordCount()
  let lnum = 1
  let n = 0
  while lnum <= line('$')
    let n = n + len(split(getline(lnum)))
    let lnum = lnum + 1
  endwhile
  return n
endfunction

Of course, like the others, you'll need to:

:set statusline=wc:%{WordCount()}

I'm sure this can be cleaned up by somebody to make it more vimmy (s:n instead of just n?), but I believe the basic functionality is there.

Edit:

Looking at this again, I really like Mikael Jansson's solution. I don't like shelling out to wc (not portable and perhaps slow). If we replace his UpdateWordCount function with the code I have above (renaming my function to UpdateWordCount), then I think we have a better solution.

Answer 7

My suggestion:

function! UpdateWordCount()
  let b:word_count = eval(join(map(getline("1", "$"), "len(split(v:val, '\\s\\+'))"), "+"))
endfunction

augroup UpdateWordCount
  au!
  autocmd BufRead,BufNewFile,BufEnter,CursorHold,CursorHoldI,InsertEnter,InsertLeave * call UpdateWordCount()
augroup END

let &statusline='wc:%{get(b:, "word_count", 0)}'

I'm not sure how this compares in speed to some of the other solutions, but it's certainly a lot simpler than most.