Update

autoload/vital/_crystal/Data/List.vim

@@ -1,5 +1,14 @@
 if !exists('g:polyglot_disabled') || index(g:polyglot_disabled, 'crystal') == -1
   
+" ___vital___
+" NOTE: lines between '" ___vital___' is generated by :Vitalize.
+" Do not mofidify the code nor insert new lines before '" ___vital___'
+function! s:_SID() abort
+  return matchstr(expand('<sfile>'), '<SNR>\zs\d\+\ze__SID$')
+endfunction
+execute join(['function! vital#_crystal#Data#List#import() abort', printf("return map({'combinations': '', 'and': '', 'sort_by': '', 'foldr1': '', 'sort': '', 'flatten': '', 'has_index': '', 'find_indices': '', 'any': '', 'unshift': '', 'span': '', 'pop': '', 'binary_search': '', 'uniq_by': '', 'or': '', 'all': '', 'zip': '', 'find_last_index': '', 'find': '', 'partition': '', 'shift': '', 'permutations': '', 'break': '', 'max_by': '', 'foldl': '', 'foldr': '', 'find_index': '', 'drop_while': '', 'group_by': '', 'take_while': '', 'conj': '', 'push': '', 'char_range': '', 'cons': '', 'foldl1': '', 'intersect': '', 'concat': '', 'map_accum': '', 'clear': '', 'has_common_items': '', 'product': '', 'zip_fill': '', 'uniq': '', 'has': '', 'min_by': '', 'with_index': ''}, \"vital#_crystal#function('<SNR>%s_' . v:key)\")", s:_SID()), 'endfunction'], "\n")
+delfunction s:_SID
+" ___vital___
 " Utilities for list.
 
 let s:save_cpo = &cpo
@@ -175,6 +184,11 @@ function! s:take_while(f, xs) abort
   return s:span(a:f, a:xs)[0]
 endfunction
 
+" similar to Haskell's Data.List.dropWhile
+function! s:drop_while(f, xs) abort
+  return s:span(a:f, a:xs)[1]
+endfunction
+
 " similar to Haskell's Data.List.partition
 function! s:partition(f, xs) abort
   return [filter(copy(a:xs), a:f), filter(copy(a:xs), '!(' . a:f . ')')]
@@ -271,14 +285,22 @@ endfunction
 
 " similar to Ruby's detect or Haskell's find.
 function! s:find(list, default, f) abort
+  let l:Call = type(a:f) is type(function('function'))
+  \          ? function('call')
+  \          : function('s:_call_string_expr')
+
   for x in a:list
-    if eval(substitute(a:f, 'v:val', string(x), 'g'))
+    if l:Call(a:f, [x])
       return x
     endif
   endfor
   return a:default
 endfunction
 
+function! s:_call_string_expr(expr, args) abort
+  return map([a:args[0]], a:expr)[0]
+endfunction
+
 " Returns the index of the first element which satisfies the given expr.
 function! s:find_index(xs, f, ...) abort
   let len = len(a:xs)
@@ -426,7 +448,7 @@ function! s:combinations(list, r) abort
   if a:r > len(a:list)
     return []
   elseif a:r < 0
-    throw 'vital: Data:List: {r} must be non-negative integer'
+    throw 'vital: Data.List: {r} must be non-negative integer'
   endif
   let n = len(a:list)
   let result = []