Haskell stuff for Vim

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+"
+" use haddock docs and index files
+" show documentation, complete & qualify identifiers 
+"
+" (Claus Reinke; last modified: 30/04/2009)
+" 
+" part of haskell plugins: http://projects.haskell.org/haskellmode-vim
+" please send patches to <claus.reinke@talk21.com>
+
+" :Doc <name> and :IDoc <name> open haddocks for <name> in opera
+"
+"   :Doc needs qualified name (default Prelude) and package (default base)
+"   :IDoc needs unqualified name, looks up possible links in g:haddock_index
+"
+"   :DocIndex populates g:haddock_index from haddock's index files
+"   :ExportDocIndex saves g:haddock_index to cache file
+"   :ImportDocIndex reloads g:haddock_index from cache file
+"
+" all the following use the haddock index (g:haddock_index)
+"
+" _? opens haddocks for unqualified name under cursor, 
+"    suggesting alternative full qualifications in popup menu
+"
+" _. fully qualifies unqualified name under cursor,
+"    suggesting alternative full qualifications in popup menu
+"
+" _i  add import <module>(<name>) statement for unqualified <name> under cursor,
+" _im add import <module>         statement for unqualified <name> under cursor,
+"    suggesting alternative full qualifications in popup menu
+"    (this currently adds one statement per call, instead of
+"     merging into existing import statements, but it's a start;-)
+"
+" CTRL-X CTRL-U (user-defined insert mode completion) 
+"   suggests completions of unqualified names in popup menu
+
+let s:scriptname = "haskell_doc.vim"
+
+" script parameters
+"   g:haddock_browser            *mandatory* which browser to call
+"   g:haddock_browser_callformat [optional] how to call browser
+"   g:haddock_indexfiledir       [optional] where to put 'haddock_index.vim'
+"   g:haddock_docdir             [optional] where to find html docs
+"   g:ghc                        [optional] which ghc to call
+"   g:ghc_pkg                    [optional] which ghc_pkg to call
+
+" been here before?
+if exists("g:haddock_index")
+  finish
+endif
+
+" initialise nested dictionary, to be populated 
+" - from haddock index files via :DocIndex
+" - from previous cached version via :ImportDocIndex
+let g:haddock_index = {}
+
+" initialise dictionary, mapping modules with haddocks to their packages,
+" populated via MkHaddockModuleIndex() or HaveModuleIndex()
+let g:haddock_moduleindex = {}
+
+" program to open urls, please set this in your vimrc
+  "examples (for windows):
+  "let g:haddock_browser = "C:/Program Files/Opera/Opera.exe"
+  "let g:haddock_browser = "C:/Program Files/Mozilla Firefox/firefox.exe"
+  "let g:haddock_browser = "C:/Program Files/Internet Explorer/IEXPLORE.exe"
+if !exists("g:haddock_browser")
+  echoerr s:scriptname." WARNING: please set g:haddock_browser!"
+endif
+
+if (!exists("g:ghc") || !executable(g:ghc)) 
+  if !executable('ghc') 
+    echoerr s:scriptname." can't find ghc. please set g:ghc, or extend $PATH"
+    finish
+  else
+    let g:ghc = 'ghc'
+  endif
+endif    
+
+if (!exists("g:ghc_pkg") || !executable(g:ghc_pkg))
+  let g:ghc_pkg = substitute(g:ghc,'\(.*\)ghc','\1ghc-pkg','')
+endif
+
+if exists("g:haddock_docdir") && isdirectory(g:haddock_docdir)
+  let s:docdir = g:haddock_docdir
+elseif executable(g:ghc_pkg)
+" try to figure out location of html docs
+" first choice: where the base docs are (from the first base listed)
+  let [field;x] = split(system(g:ghc_pkg . ' field base haddock-html'),'\n')
+  let field = substitute(field,'haddock-html: \(.*\)libraries.base','\1','')
+  let field = substitute(field,'\\','/','g')
+  let alternate = substitute(field,'html','doc/html','')
+  if isdirectory(field)
+    let s:docdir = field
+  elseif isdirectory(alternate)
+    let s:docdir = alternate
+  endif
+else
+  echoerr s:scriptname." can't find ghc-pkg (set g:ghc_pkg ?)."
+endif
+
+" second choice: try some known suspects for windows/unix
+if !exists('s:docdir') || !isdirectory(s:docdir)
+  let s:ghc_libdir = substitute(system(g:ghc . ' --print-libdir'),'\n','','')
+  let location1a = s:ghc_libdir . '/doc/html/'
+  let location1b = s:ghc_libdir . '/doc/'
+  let s:ghc_version = substitute(system(g:ghc . ' --numeric-version'),'\n','','')
+  let location2 = '/usr/share/doc/ghc-' . s:ghc_version . '/html/' 
+  if isdirectory(location1a)
+    let s:docdir = location1a
+  elseif isdirectory(location1b)
+    let s:docdir = location1b
+  elseif isdirectory(location2)
+    let s:docdir = location2
+  else " give up
+    echoerr s:scriptname." can't find locaton of html documentation (set g:haddock_docdir)."
+    finish
+  endif
+endif
+
+" todo: can we turn s:docdir into a list of paths, and
+" include docs for third-party libs as well?
+
+let s:libraries         = s:docdir . 'libraries/'
+let s:guide             = s:docdir . 'users_guide/'
+let s:index             = 'index.html'
+if exists("g:haddock_indexfiledir") && filewritable(g:haddock_indexfiledir)
+  let s:haddock_indexfiledir = g:haddock_indexfiledir 
+elseif filewritable(s:libraries)
+  let s:haddock_indexfiledir = s:libraries
+elseif filewritable($HOME)
+  let s:haddock_indexfiledir = $HOME.'/'
+else "give up
+  echoerr s:scriptname." can't locate index file. please set g:haddock_indexfiledir"
+  finish
+endif
+let s:haddock_indexfile = s:haddock_indexfiledir . 'haddock_index.vim'
+
+" different browser setups require different call formats;
+" you might want to call the browser synchronously or 
+" asynchronously, and the latter is os-dependent;
+"
+" by default, the browser is started in the background when on 
+" windows or if running in a gui, and in the foreground otherwise
+" (eg, console-mode for remote sessions, with text-mode browsers).
+"
+" you can override these defaults in your vimrc, via a format 
+" string including 2 %s parameters (the first being the browser 
+" to call, the second being the url).
+if !exists("g:haddock_browser_callformat")
+  if has("win32") || has("win64")
+    let g:haddock_browser_callformat = 'start %s "%s"'
+  else
+    if has("gui_running")
+      let g:haddock_browser_callformat = '%s %s '.printf(&shellredir,'/dev/null').' &'
+    else
+      let g:haddock_browser_callformat = '%s %s'
+    endif
+  endif
+endif
+
+" allow map leader override
+if !exists("maplocalleader")
+  let maplocalleader='_'
+endif
+
+command! DocSettings call DocSettings()
+function! DocSettings()
+  for v in ["g:haddock_browser","g:haddock_browser_callformat","g:haddock_docdir","g:haddock_indexfiledir","s:ghc_libdir","s:ghc_version","s:docdir","s:libraries","s:guide","s:haddock_indexfile"]
+    if exists(v)
+      echo v '=' eval(v)
+    else
+      echo v '='
+    endif
+  endfor
+endfunction
+
+function! DocBrowser(url)
+  "echomsg "DocBrowser(".url.")"
+  if (!exists("g:haddock_browser") || !executable(g:haddock_browser))
+    echoerr s:scriptname." can't find documentation browser. please set g:haddock_browser"
+    return
+  endif
+  " start browser to open url, according to specified format
+  let url = a:url=~'^\(file://\|http://\)' ? a:url : 'file://'.a:url
+  silent exe '!'.printf(g:haddock_browser_callformat,g:haddock_browser,escape(url,'#%')) 
+endfunction
+
+"Doc/Doct are an old interface for documentation lookup
+"(that is the reason they are not documented!-)
+"
+"These uses are still fine at the moment, and are the reason 
+"that this command still exists at all
+"
+" :Doc -top
+" :Doc -libs
+" :Doc -guide
+"
+"These uses may or may not work, and shouldn't be relied on anymore
+"(usually, you want _?/_?1/_?2 or :MDoc; there is also :IDoc)
+"
+" :Doc length
+" :Doc Control.Monad.when
+" :Doc Data.List.
+" :Doc Control.Monad.State.runState mtl
+command! -nargs=+ Doc  call Doc('v',<f-args>)
+command! -nargs=+ Doct call Doc('t',<f-args>)
+
+function! Doc(kind,qualname,...) 
+  let suffix   = '.html'
+  let relative = '#'.a:kind.'%3A'
+
+  if a:qualname=="-top"
+    call DocBrowser(s:docdir . s:index)
+    return
+  elseif a:qualname=="-libs"
+    call DocBrowser(s:libraries . s:index)
+    return
+  elseif a:qualname=="-guide"
+    call DocBrowser(s:guide . s:index)
+    return
+  endif
+
+  if a:0==0 " no package specified
+    let package = 'base/'
+  else
+    let package = a:1 . '/'
+  endif
+
+  if match(a:qualname,'\.')==-1 " unqualified name
+    let [qual,name] = [['Prelude'],a:qualname]
+    let file = join(qual,'-') . suffix . relative . name
+  elseif a:qualname[-1:]=='.' " module qualifier only
+    let parts = split(a:qualname,'\.')
+    let quallen = len(parts)-1
+    let [qual,name] = [parts[0:quallen],parts[-1]]
+    let file = join(qual,'-') . suffix
+  else " qualified name
+    let parts = split(a:qualname,'\.')
+    let quallen = len(parts)-2
+    let [qual,name] = [parts[0:quallen],parts[-1]]
+    let file = join(qual,'-') . suffix . relative . name
+  endif
+
+  let path = s:libraries . package . file
+  call DocBrowser(path)
+endfunction
+
+" TODO: add commandline completion for :IDoc
+"       switch to :emenu instead of inputlist?
+" indexed variant of Doc, looking up links in g:haddock_index
+" usage:
+"  1. :IDoc length
+"  2. click on one of the choices, or select by number (starting from 0)
+command! -nargs=+ IDoc call IDoc(<f-args>)
+function! IDoc(name,...) 
+  let choices = HaddockIndexLookup(a:name)
+  if choices=={} | return | endif
+  if a:0==0
+    let keylist = map(deepcopy(keys(choices)),'substitute(v:val,"\\[.\\]","","")')
+    let choice = inputlist(keylist)
+  else
+    let choice = a:1
+  endif
+  let path = values(choices)[choice] " assumes same order for keys/values..
+  call DocBrowser(path)
+endfunction
+
+let s:flagref = s:guide . 'flag-reference.html'
+if filereadable(s:flagref)
+  " extract the generated fragment ids for the 
+  " flag reference sections 
+  let s:headerPat     = '.\{-}<h3 class="title"><a name="\([^"]*\)"><\/a>\([^<]*\)<\/h3>\(.*\)'
+  let s:flagheaders   = []
+  let s:flagheaderids = {}
+  let s:contents      = join(readfile(s:flagref))
+  let s:ml = matchlist(s:contents,s:headerPat)
+  while s:ml!=[]
+    let [_,s:id,s:title,s:r;s:x] = s:ml
+    let s:flagheaders            = add(s:flagheaders, s:title)
+    let s:flagheaderids[s:title] = s:id
+    let s:ml = matchlist(s:r,s:headerPat)
+  endwhile
+  command! -nargs=1 -complete=customlist,CompleteFlagHeaders FlagReference call FlagReference(<f-args>)
+  function! FlagReference(section)
+    let relativeUrl = a:section==""||!exists("s:flagheaderids['".a:section."']") ? 
+                    \ "" : "#".s:flagheaderids[a:section]
+    call DocBrowser(s:flagref.relativeUrl)
+  endfunction
+  function! CompleteFlagHeaders(al,cl,cp)
+    let s:choices = s:flagheaders
+    return CompleteAux(a:al,a:cl,a:cp)
+  endfunction
+endif
+
+command! -nargs=1 -complete=customlist,CompleteHaddockModules MDoc call MDoc(<f-args>)
+function! MDoc(module)
+  let suffix   = '.html'
+  call HaveModuleIndex()
+  if !has_key(g:haddock_moduleindex,a:module)
+    echoerr a:module 'not found in haddock module index'
+    return
+  endif
+  let package = g:haddock_moduleindex[a:module]['package']
+  let file    = substitute(a:module,'\.','-','g') . suffix
+" let path    = s:libraries . package . '/' . file
+  let path    = g:haddock_moduleindex[a:module]['html']
+  call DocBrowser(path)
+endfunction
+
+function! CompleteHaddockModules(al,cl,cp)
+  call HaveModuleIndex()
+  let s:choices = keys(g:haddock_moduleindex)
+  return CompleteAux(a:al,a:cl,a:cp)
+endfunction
+
+" create a dictionary g:haddock_index, containing the haddoc index
+command! DocIndex call DocIndex()
+function! DocIndex()
+  let files   = split(globpath(s:libraries,'doc-index*.html'),'\n')
+  let g:haddock_index = {}
+  call ProcessHaddockIndexes2(s:libraries,files)
+  if GHC_VersionGE([6,8,2])
+    if &shell =~ 'sh' " unix-type shell
+      let s:addon_libraries = split(system(g:ghc_pkg . ' field \* haddock-html'),'\n')
+    else " windows cmd.exe and the like
+      let s:addon_libraries = split(system(g:ghc_pkg . ' field * haddock-html'),'\n')
+    endif
+    for addon in s:addon_libraries
+      let ml = matchlist(addon,'haddock-html: \("\)\?\(file:///\)\?\([^"]*\)\("\)\?')
+      if ml!=[]
+        let [_,quote,file,addon_path;x] = ml
+        let addon_path = substitute(addon_path,'\(\\\\\|\\\)','/','g')
+        let addon_files = split(globpath(addon_path,'doc-index*.html'),'\n')
+        call ProcessHaddockIndexes2(addon_path,addon_files)
+      endif
+    endfor
+  endif
+  return 1
+endfunction
+
+function! ProcessHaddockIndexes(location,files)
+  let entryPat= '.\{-}"indexentry"[^>]*>\([^<]*\)<\(\%([^=]\{-}TD CLASS="\%(indexentry\)\@!.\{-}</TD\)*\)[^=]\{-}\(\%(="indexentry\|TABLE\).*\)'
+  let linkPat = '.\{-}HREF="\([^"]*\)".>\([^<]*\)<\(.*\)'
+
+  redraw
+  echo 'populating g:haddock_index from haddock index files in ' a:location
+  for f in a:files  
+    echo f[len(a:location):]
+    let contents = join(readfile(f))
+    let ml = matchlist(contents,entryPat)
+    while ml!=[]
+      let [_,entry,links,r;x] = ml
+      "echo entry links
+      let ml2 = matchlist(links,linkPat)
+      let link = {}
+      while ml2!=[]
+        let [_,l,m,links;x] = ml2
+        "echo l m
+        let link[m] = a:location . '/' . l
+        let ml2 = matchlist(links,linkPat)
+      endwhile
+      let g:haddock_index[DeHTML(entry)] = deepcopy(link)
+      "echo entry g:haddock_index[entry]
+      let ml = matchlist(r,entryPat)
+    endwhile
+  endfor
+endfunction
+
+" concatenating all lines is too slow for a big file, process lines directly
+function! ProcessHaddockIndexes2(location,files)
+  let entryPat= '^>\([^<]*\)</'
+  let linkPat = '.\{-}A HREF="\([^"]*\)"'
+  let kindPat = '#\(.\)'
+
+  " redraw
+  echo 'populating g:haddock_index from haddock index files in ' a:location
+  for f in a:files  
+    echo f[len(a:location):]
+    let isEntry = 0
+    let isLink  = ''
+    let link    = {}
+    let entry   = ''
+    for line in readfile(f)
+      if line=~'CLASS="indexentry' 
+        if (link!={}) && (entry!='')
+          if has_key(g:haddock_index,DeHTML(entry))
+            let dict = extend(g:haddock_index[DeHTML(entry)],deepcopy(link))
+          else
+            let dict = deepcopy(link)
+          endif
+          let g:haddock_index[DeHTML(entry)] = dict
+          let link  = {}
+          let entry = ''
+        endif
+        let isEntry=1 
+        continue 
+      endif
+      if isEntry==1
+        let ml = matchlist(line,entryPat)
+        if ml!=[] | let [_,entry;x] = ml | let isEntry=0 | continue | endif
+      endif
+      if entry!=''
+        let ml = matchlist(line,linkPat)
+        if ml!=[] | let [_,isLink;x]=ml | continue | endif
+      endif
+      if isLink!=''
+        let ml = matchlist(line,entryPat)
+        if ml!=[] 
+          let [_,module;x] = ml 
+          let [_,kind;x]   = matchlist(isLink,kindPat)
+          let last         = a:location[strlen(a:location)-1]
+          let link[module."[".kind."]"] = a:location . (last=='/'?'':'/') . isLink
+          let isLink='' 
+          continue 
+        endif
+      endif
+    endfor
+    if link!={} 
+      if has_key(g:haddock_index,DeHTML(entry))
+        let dict = extend(g:haddock_index[DeHTML(entry)],deepcopy(link))
+      else
+        let dict = deepcopy(link)
+      endif
+      let g:haddock_index[DeHTML(entry)] = dict
+    endif
+  endfor
+endfunction
+
+command! ExportDocIndex call ExportDocIndex()
+function! ExportDocIndex()
+  call HaveIndex()
+  let entries = []
+  for key in keys(g:haddock_index)
+    let entries += [key,string(g:haddock_index[key])]
+  endfor
+  call writefile(entries,s:haddock_indexfile)
+  redir end
+endfunction
+
+command! ImportDocIndex call ImportDocIndex()
+function! ImportDocIndex()
+  if filereadable(s:haddock_indexfile)
+    let lines = readfile(s:haddock_indexfile)
+    let i=0
+    while i<len(lines)
+      let [key,dict] = [lines[i],lines[i+1]]
+      sandbox let g:haddock_index[key] = eval(dict) 
+      let i+=2
+    endwhile
+    return 1
+  else
+    return 0
+  endif
+endfunction
+
+function! HaveIndex()
+  return (g:haddock_index!={} || ImportDocIndex() || DocIndex() )
+endfunction
+
+function! MkHaddockModuleIndex()
+  let g:haddock_moduleindex = {}
+  call HaveIndex()
+  for key in keys(g:haddock_index)
+    let dict = g:haddock_index[key]
+    for module in keys(dict)
+      let html = dict[module]
+      let html   = substitute(html  ,'#.*$','','')
+      let module = substitute(module,'\[.\]','','')
+      let ml = matchlist(html,'libraries/\([^\/]*\)\/')
+      if ml!=[]
+        let [_,package;x] = ml
+        let g:haddock_moduleindex[module] = {'package':package,'html':html}
+      endif
+      let ml = matchlist(html,'/\([^\/]*\)\/html/[A-Z]')
+      if ml!=[]
+        let [_,package;x] = ml
+        let g:haddock_moduleindex[module] = {'package':package,'html':html}
+      endif
+    endfor
+  endfor
+endfunction
+
+function! HaveModuleIndex()
+  return (g:haddock_moduleindex!={} || MkHaddockModuleIndex() )
+endfunction
+
+" decode HTML symbol encodings (are these all we need?)
+function! DeHTML(entry)
+  let res = a:entry
+  let decode = { '&lt;': '<', '&gt;': '>', '&amp;': '\\&' }
+  for enc in keys(decode)
+    exe 'let res = substitute(res,"'.enc.'","'.decode[enc].'","g")'
+  endfor
+  return res
+endfunction
+
+" find haddocks for word under cursor
+" also lists possible definition sites
+" - needs to work for both qualified and unqualified items
+" - for 'import qualified M as A', consider M.item as source of A.item
+" - offer sources from both type [t] and value [v] namespaces
+" - for unqualified items, list all possible sites
+" - for qualified items, list imported sites only
+" keep track of keys with and without namespace tags:
+" the former are needed for lookup, the latter for matching against source
+map <LocalLeader>? :call Haddock()<cr>
+function! Haddock()
+  amenu ]Popup.- :echo '-'<cr>
+  aunmenu ]Popup
+  let namsym   = haskellmode#GetNameSymbol(getline('.'),col('.'),0)
+  if namsym==[]
+    redraw
+    echo 'no name/symbol under cursor!'
+    return 0
+  endif
+  let [start,symb,qual,unqual] = namsym
+  let imports = haskellmode#GatherImports()
+  let asm  = has_key(imports[1],qual) ? imports[1][qual]['modules'] : []
+  let name = unqual
+  let dict = HaddockIndexLookup(name)
+  if dict=={} | return | endif
+  " for qualified items, narrow results to possible imports that provide qualifier
+  let filteredKeys = filter(copy(keys(dict))
+                         \ ,'match(asm,substitute(v:val,''\[.\]'','''',''''))!=-1') 
+  let keys = (qual!='') ?  filteredKeys : keys(dict)
+  if (keys==[]) && (qual!='')
+    echoerr qual.'.'.unqual.' not found in imports'
+    return 0
+  endif
+  " use 'setlocal completeopt+=menuone' if you always want to see menus before
+  " anything happens (I do, but many users don't..)
+  if len(keys)==1 && (&completeopt!~'menuone')
+        call DocBrowser(dict[keys[0]])
+  elseif has("gui_running")
+    for key in keys
+      exe 'amenu ]Popup.'.escape(key,'\.').' :call DocBrowser('''.dict[key].''')<cr>'
+    endfor
+    popup ]Popup
+  else
+    let s:choices = keys
+    let key = input('browse docs for '.name.' in: ','','customlist,CompleteAux')
+    if key!=''
+      call DocBrowser(dict[key])
+    endif
+  endif
+endfunction
+
+if !exists("g:haskell_search_engines")
+  let g:haskell_search_engines = 
+    \ {'hoogle':'http://www.haskell.org/hoogle/?hoogle=%s'
+    \ ,'hayoo!':'http://holumbus.fh-wedel.de/hayoo/hayoo.html?query=%s'
+    \ }
+endif
+
+map <LocalLeader>?? :let es=g:haskell_search_engines
+                 \ \|echo "g:haskell_search_engines"
+                 \ \|for e in keys(es)
+                 \ \|echo e.' : '.es[e]
+                 \ \|endfor<cr>
+map <LocalLeader>?1 :call HaskellSearchEngine('hoogle')<cr>
+map <LocalLeader>?2 :call HaskellSearchEngine('hayoo!')<cr>
+
+" query one of the Haskell search engines for the thing under cursor
+" - unqualified symbols need to be url-escaped
+" - qualified ids need to be fed as separate qualifier and id for
+"   both hoogle (doesn't handle qualified symbols) and hayoo! (no qualified
+"   ids at all)
+" - qualified ids referring to import-qualified-as qualifiers need to be
+"   translated to the multi-module searches over the list of original modules
+function! HaskellSearchEngine(engine)
+  amenu ]Popup.- :echo '-'<cr>
+  aunmenu ]Popup
+  let namsym   = haskellmode#GetNameSymbol(getline('.'),col('.'),0)
+  if namsym==[]
+    redraw
+    echo 'no name/symbol under cursor!'
+    return 0
+  endif
+  let [start,symb,qual,unqual] = namsym
+  let imports = haskellmode#GatherImports()
+  let asm  = has_key(imports[1],qual) ? imports[1][qual]['modules'] : []
+  let unqual = haskellmode#UrlEncode(unqual)
+  if a:engine=='hoogle'
+    let name = asm!=[] ? unqual.'+'.join(map(copy(asm),'"%2B".v:val'),'+')
+           \ : qual!='' ? unqual.'+'.haskellmode#UrlEncode('+').qual
+           \ : unqual
+  elseif a:engine=='hayoo!'
+    let name = asm!=[] ? unqual.'+module:('.join(copy(asm),' OR ').')'
+           \ : qual!='' ? unqual.'+module:'.qual
+           \ : unqual
+  else
+    let name = qual=="" ? unqual : qual.".".unqual
+  endif
+  if has_key(g:haskell_search_engines,a:engine)
+    call DocBrowser(printf(g:haskell_search_engines[a:engine],name))
+  else
+    echoerr "unknown search engine: ".a:engine
+  endif
+endfunction
+
+" used to pass on choices to CompleteAux
+let s:choices=[]
+
+" if there's no gui, use commandline completion instead of :popup
+" completion function CompleteAux suggests completions for a:al, wrt to s:choices
+function! CompleteAux(al,cl,cp)
+  "echomsg '|'.a:al.'|'.a:cl.'|'.a:cp.'|'
+  let res = []
+  let l = len(a:al)-1
+  for r in s:choices
+    if l==-1 || r[0 : l]==a:al
+      let res += [r]
+    endif
+  endfor
+  return res
+endfunction
+
+" CamelCase shorthand matching: 
+" favour upper-case letters and module qualifier separators (.) for disambiguation
+function! CamelCase(shorthand,string)
+  let s1 = a:shorthand
+  let s2 = a:string
+  let notFirst = 0 " don't elide before first pattern letter
+  while ((s1!="")&&(s2!="")) 
+    let head1 = s1[0]
+    let head2 = s2[0]
+    let elide = notFirst && ( ((head1=~'[A-Z]') && (head2!~'[A-Z.]')) 
+              \             ||((head1=='.') && (head2!='.')) ) 
+    if elide
+      let s2=s2[1:]
+    elseif (head1==head2) 
+      let s1=s1[1:]
+      let s2=s2[1:]
+    else
+      return 0
+    endif
+    let notFirst = (head1!='.')||(head2!='.') " treat separators as new beginnings
+  endwhile
+  return (s1=="")
+endfunction
+
+" use haddock name index for insert mode completion (CTRL-X CTRL-U)
+function! CompleteHaddock(findstart, base)
+  if a:findstart 
+    let namsym   = haskellmode#GetNameSymbol(getline('.'),col('.'),-1) " insert-mode: we're 1 beyond the text
+    if namsym==[]
+      redraw
+      echo 'no name/symbol under cursor!'
+      return -1
+    endif
+    let [start,symb,qual,unqual] = namsym
+    return (start-1)
+  else " find keys matching with "a:base"
+    let res  = []
+    let l    = len(a:base)-1
+    let qual = a:base =~ '^[A-Z][a-zA-Z0-9_'']*\(\.[A-Z][a-zA-Z0-9_'']*\)*\(\.[a-zA-Z0-9_'']*\)\?$'
+    call HaveIndex() 
+    for key in keys(g:haddock_index)
+      let keylist = map(deepcopy(keys(g:haddock_index[key])),'substitute(v:val,"\\[.\\]","","")')
+      if (key[0 : l]==a:base)
+        for m in keylist
+          let res += [{"word":key,"menu":m,"dup":1}]
+        endfor
+      elseif qual " this tends to be slower
+        for m in keylist
+          let word = m . '.' . key
+          if word[0 : l]==a:base
+            let res += [{"word":word,"menu":m,"dup":1}]
+          endif
+        endfor
+      endif
+    endfor
+    if res==[] " no prefix matches, try CamelCase shortcuts
+      for key in keys(g:haddock_index)
+        let keylist = map(deepcopy(keys(g:haddock_index[key])),'substitute(v:val,"\\[.\\]","","")')
+        if CamelCase(a:base,key)
+          for m in keylist
+            let res += [{"word":key,"menu":m,"dup":1}]
+          endfor
+        elseif qual " this tends to be slower
+          for m in keylist
+            let word = m . '.' . key
+            if CamelCase(a:base,word)
+              let res += [{"word":word,"menu":m,"dup":1}]
+            endif
+          endfor
+        endif
+      endfor
+    endif
+    return res
+  endif
+endfunction
+setlocal completefunc=CompleteHaddock
+"
+" Vim's default completeopt is menu,preview
+" you probably want at least menu, or you won't see alternatives listed
+" setlocal completeopt+=menu
+
+" menuone is useful, but other haskellmode menus will try to follow your choice here in future
+" setlocal completeopt+=menuone
+
+" longest sounds useful, but doesn't seem to do what it says, and interferes with CTRL-E
+" setlocal completeopt-=longest
+
+" fully qualify an unqualified name
+" TODO: - standardise commandline versions of menus
+map <LocalLeader>. :call Qualify()<cr>
+function! Qualify()
+  amenu ]Popup.- :echo '-'<cr>
+  aunmenu ]Popup
+  let namsym   = haskellmode#GetNameSymbol(getline('.'),col('.'),0)
+  if namsym==[]
+    redraw
+    echo 'no name/symbol under cursor!'
+    return 0
+  endif
+  let [start,symb,qual,unqual] = namsym
+  if qual!=''  " TODO: should we support re-qualification?
+    redraw
+    echo 'already qualified'
+    return 0
+  endif
+  let name = unqual
+  let line         = line('.')
+  let prefix       = (start<=1 ? '' : getline(line)[0:start-2] )
+  let dict   = HaddockIndexLookup(name)
+  if dict=={} | return | endif
+  let keylist = map(deepcopy(keys(dict)),'substitute(v:val,"\\[.\\]","","")')
+  let imports = haskellmode#GatherImports()
+  let qualifiedImports = []
+  for qualifiedImport in keys(imports[1])
+    let c=0
+    for module in imports[1][qualifiedImport]['modules']
+      if haskellmode#ListElem(keylist,module) | let c+=1 | endif
+    endfor
+    if c>0 | let qualifiedImports=[qualifiedImport]+qualifiedImports | endif
+  endfor
+  "let asm  = has_key(imports[1],qual) ? imports[1][qual]['modules'] : []
+  let keylist = filter(copy(keylist),'index(qualifiedImports,v:val)==-1')
+  if has("gui_running")
+    " amenu ]Popup.-imported- :
+    for key in qualifiedImports
+      let lhs=escape(prefix.name,'/.|\')
+      let rhs=escape(prefix.key.'.'.name,'/&|\')
+      exe 'amenu ]Popup.'.escape(key,'\.').' :'.line.'s/'.lhs.'/'.rhs.'/<cr>:noh<cr>'
+    endfor
+    amenu ]Popup.-not\ imported- :
+    for key in keylist
+      let lhs=escape(prefix.name,'/.|\')
+      let rhs=escape(prefix.key.'.'.name,'/&|\')
+      exe 'amenu ]Popup.'.escape(key,'\.').' :'.line.'s/'.lhs.'/'.rhs.'/<cr>:noh<cr>'
+    endfor
+    popup ]Popup
+  else
+    let s:choices = qualifiedImports+keylist
+    let key = input('qualify '.name.' with: ','','customlist,CompleteAux')
+    if key!=''
+      let lhs=escape(prefix.name,'/.\')
+      let rhs=escape(prefix.key.'.'.name,'/&\')
+      exe line.'s/'.lhs.'/'.rhs.'/'
+      noh
+    endif
+  endif
+endfunction
+
+" create (qualified) import for a (qualified) name
+" TODO: refine search patterns, to avoid misinterpretation of
+"       oddities like import'Neither or not'module
+map <LocalLeader>i :call Import(0,0)<cr>
+map <LocalLeader>im :call Import(1,0)<cr>
+map <LocalLeader>iq :call Import(0,1)<cr>
+map <LocalLeader>iqm :call Import(1,1)<cr>
+function! Import(module,qualified)
+  amenu ]Popup.- :echo '-'<cr>
+  aunmenu ]Popup
+  let namsym   = haskellmode#GetNameSymbol(getline('.'),col('.'),0)
+  if namsym==[]
+    redraw
+    echo 'no name/symbol under cursor!'
+    return 0
+  endif
+  let [start,symb,qual,unqual] = namsym
+  let name       = unqual
+  let pname      = ( symb ? '('.name.')' : name )
+  let importlist = a:module ? '' : '('.pname.')'
+  let qualified  = a:qualified ? 'qualified ' : ''
+
+  if qual!=''
+    exe 'call append(search(''\%1c\(\<import\>\|\<module\>\|{-# OPTIONS\|{-# LANGUAGE\)'',''nb''),''import '.qualified.qual.importlist.''')'
+    return
+  endif
+
+  let line   = line('.')
+  let prefix = getline(line)[0:start-1]
+  let dict   = HaddockIndexLookup(name)
+  if dict=={} | return | endif
+  let keylist = map(deepcopy(keys(dict)),'substitute(v:val,"\\[.\\]","","")')
+  if has("gui_running")
+    for key in keylist
+      " exe 'amenu ]Popup.'.escape(key,'\.').' :call append(search("\\%1c\\(import\\\\|module\\\\|{-# OPTIONS\\)","nb"),"import '.key.importlist.'")<cr>'
+      exe 'amenu ]Popup.'.escape(key,'\.').' :call append(search(''\%1c\(\<import\>\\|\<module\>\\|{-# OPTIONS\\|{-# LANGUAGE\)'',''nb''),''import '.qualified.key.escape(importlist,'|').''')<cr>'
+    endfor
+    popup ]Popup
+  else
+    let s:choices = keylist
+    let key = input('import '.name.' from: ','','customlist,CompleteAux')
+    if key!=''
+      exe 'call append(search(''\%1c\(\<import\>\|\<module\>\|{-# OPTIONS\|{-# LANGUAGE\)'',''nb''),''import '.qualified.key.importlist.''')'
+    endif
+  endif
+endfunction
+
+function! HaddockIndexLookup(name)
+  call HaveIndex()
+  if !has_key(g:haddock_index,a:name)
+    echoerr a:name 'not found in haddock index'
+    return {}
+  endif
+  return g:haddock_index[a:name]
+endfunction
+
+" copied from ghc.vim :-( should we move everything to using autoload instead?
+" we query the ghc version here, as we don't otherwise need it..
+function! GHC_VersionGE(target)
+  let s:ghc_version = substitute(system(g:ghc . ' --numeric-version'),'\n','','')
+  let current = split(g:ghc_version, '\.' )
+  let target  = a:target
+  for i in current
+    if ((target==[]) || (i>target[0]))
+      return 1
+    elseif (i==target[0])
+      let target = target[1:]
+    else
+      return 0
+    endif
+  endfor
+  return 1
+endfunction