vim: count how many buffers been modified?

Question

Pursuing a vimscript function or expression that

count how many buffers been modified.

i.e., how many buffers :bm could switch to,

given that option hidden is set.

== Edit ==

In the hope of used in statusline.

Answer 1

Found it.

func! CountModifiedBuffer()
    let mod = map(getbufinfo(), 'v:val.changed')
    return len(filter(mod, 'v:val'))
endfunc

== Edit ==

I use %{IsBuffersModified()} instead of builtin %m inside my statusline setting, which encode more info.

" [+] if only current modified, [+3] if 3 modified including current buffer.
" [3] if 3 modified and current not, "" if none modified.
func! IsBuffersModified()
    let cnt = CountModifiedBuffer()
    return cnt == 0 ? "" : ( &modified ? "[+". (cnt>1?cnt:"") ."]" : "[".cnt."]" )
endfunc

== Edit Edit ==

CountModifiedBuffer could be one-liner.

    return len(filter(getbufinfo(), 'v:val.changed == 1'))