wordcount.vim

let s:S = vital#vital#import('Data.String')
let s:L = vital#vital#import('Data.List')

function! s:count_words(text) abort
  let F = { memo, x -> has_key(memo, x)
        \ ? extend(memo, {x: memo[x] + 1})
        \ : extend(memo, {x: 1})}
  return s:L.foldl(F, {}, s:S.scan(a:text, '\w\+'))
endfunction

echo s:count_words('this is a pen or not a pen')
" {'this': 1, 'is': 1, 'a': 2, 'pen': 2, ...}