Inverted index: Difference between revisions
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|> Set.intersectMany |
|> Set.intersectMany |
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searchResults |> Set.iter (printf "%s ") ; printfn "" |
printf "Found in: " ; searchResults |> Set.iter (printf "%s ") ; printfn ""</lang> |
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</lang> |
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=={{header|Go}}== |
=={{header|Go}}== |
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<lang go>package main |
<lang go>package main |
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Revision as of 10:32, 16 March 2011
You are encouraged to solve this task according to the task description, using any language you may know.
An Inverted Index is a data structure used to create full text search.
Given a set of text files, implement a program to create an inverted index. Also create a user interface to do a search using that inverted index which returns a list of files that contain the query term / terms. The search index can be in memory.
AutoHotkey
<lang AutoHotkey>; http://www.autohotkey.com/forum/viewtopic.php?t=41479 inputbox, files, files, file pattern such as c:\files\*.txt
word2docs := object() ; autohotkey_L is needed.
stime := A_tickcount Loop, %files%, 0,1 {
tooltip,%A_index% / 500 wordList := WordsIn(A_LoopFileFullPath) InvertedIndex(wordList, A_loopFileFullpath)
}
tooltip msgbox, % "total time " (A_tickcount-stime)/1000
gosub, search return
search: Loop {
InputBox, keyword , input single keyword only msgbox, % foundDocs := findword(keyword)
} return
WordsIn(docpath) {
FileRead, content, %docpath%
spos = 1
Loop
{
if !(spos := Regexmatch(content, "[a-zA-Z]{2,}",match, spos))
break
spos += strlen(match)
this_wordList .= match "`n"
}
Sort, this_wordList, U
return this_wordList
}
InvertedIndex(byref words, docpath) {
global word2docs
loop, parse, words, `n,`r
{
if A_loopField =
continue
word2docs[A_loopField] := word2docs[A_loopField] docpath "`n"
}
}
findWord(word2find) {
global word2docs
if (word2docs[word2find] = "")
return ""
else
return word2docs[word2find]
}</lang>
C#
<lang csharp>using System; using System.Collections.Generic; using System.IO; using System.Linq;
class InvertedIndex {
static Dictionary<TItem, IEnumerable<TKey>> Invert<TKey, TItem>(Dictionary<TKey, IEnumerable<TItem>> dictionary)
{
return dictionary
.SelectMany(keyValuePair => keyValuePair.Value.Select(item => new KeyValuePair<TItem, TKey>(item, keyValuePair.Key)))
.GroupBy(keyValuePair => keyValuePair.Key)
.ToDictionary(group => group.Key, group => group.Select(keyValuePair => keyValuePair.Value));
}
static void Main()
{
Console.Write("files: ");
var files = Console.ReadLine();
Console.Write("find: ");
var find = Console.ReadLine();
var dictionary = files.Split().ToDictionary(file => file, file => File.ReadAllText(file).Split().AsEnumerable());
Console.WriteLine("{0} found in: {1}", find, string.Join(" ", Invert(dictionary)[find]));
}
}</lang> Sample output: <lang>files: file1 file2 file3 find: what what found in: file1 file2</lang>
Factor
<lang factor>USING: assocs fry io.encodings.utf8 io.files kernel sequences sets splitting vectors ; IN: rosettacode.inverted-index
- file-words ( file -- assoc )
utf8 file-contents " ,;:!?.()[]{}\n\r" split harvest ;
- add-to-file-list ( files file -- files )
over [ swap [ adjoin ] keep ] [ nip 1vector ] if ;
- add-to-index ( words index file -- )
'[ _ [ _ add-to-file-list ] change-at ] each ;
- (index-files) ( files index -- )
[ [ [ file-words ] keep ] dip swap add-to-index ] curry each ;
- index-files ( files -- index )
H{ } clone [ (index-files) ] keep ;
- query ( terms index -- files )
[ at ] curry map [ ] [ intersect ] map-reduce ;
</lang>
Example use : <lang>( scratchpad ) { "f1" "f2" "f3" } index-files
--- Data stack: H{ { "a" ~vector~ } { "is" ~vector~ } { "what" ~vector~ } { ... ( scratchpad ) { "what" "is" "it" } swap query . V{ "f1" "f2" } </lang>
F#
<lang fsharp>open System open System.IO
// Map search terms to associated set of files type searchIndexMap = Map<string, Set<string>>
let inputSearchCriteria() =
let readLine prompt =
printf "%s: " prompt
Console.ReadLine().Split()
readLine "files", (readLine "find") |> Array.map (fun s -> s.ToLower())
let updateIndex indexMap keyValuePair =
let k, v = keyValuePair
match Map.tryFind k indexMap with
| None -> Map.add k (Set.singleton v) indexMap
| Some set -> Map.add k (Set.add v set) indexMap
let buildIndex files =
let fileData file =
File.ReadAllText(file).Split() |> Seq.map (fun word -> word.ToLower(), file)
files |> Seq.collect fileData
|> Seq.fold updateIndex Map.empty
let searchFiles() =
let files, terms = inputSearchCriteria() let indexes = buildIndex files
let searchResults = terms |> Seq.map (fun i -> Map.find i indexes)
|> Set.intersectMany
printf "Found in: " ; searchResults |> Set.iter (printf "%s ") ; printfn ""</lang>
Go
<lang go>package main
import (
"bytes" "encoding/line" "fmt" "os"
)
// inverted index representation var index map[string][]int // ints index into indexed var indexed []doc
type doc struct {
file string title string
}
func main() {
// initialize representation index = make(map[string][]int)
// build index
if err := indexDir("docs"); err != nil {
fmt.Println(err)
return
}
// run user interface ui()
}
func indexDir(dir string) os.Error {
df, err := os.Open(dir, os.O_RDONLY, 0)
if err != nil {
return err
}
fis, err := df.Readdir(-1)
if err != nil {
return err
}
if len(fis) == 0 {
return os.NewError(fmt.Sprintf("no files in %s", dir))
}
indexed := 0
for _, fi := range fis {
if fi.IsRegular() {
if indexFile(dir + "/" + fi.Name) {
indexed++
}
}
}
return nil
}
func indexFile(fn string) bool {
f, err := os.Open(fn, os.O_RDONLY, 0)
if err != nil {
fmt.Println(err)
return false // only false return
}
// register new file
x := len(indexed)
indexed = append(indexed, doc{fn, fn})
pdoc := &indexed[x]
// scan lines
r := line.NewReader(f, 4096)
lines := 0
for {
b, isPrefix, err := r.ReadLine()
switch {
case err == os.EOF:
return true
case err != nil:
fmt.Println(err)
return true
case isPrefix:
fmt.Printf("%s: unexpeced long line\n", fn)
return true
case lines < 20 && bytes.HasPrefix(b, []byte("Title:")):
// in a real program you would write code
// to skip the Gutenberg document header
// and not index it.
pdoc.title = string(b[7:])
}
// index line of text in b
// again, in a real program you would write a much
// nicer word splitter.
wordLoop:
for _, bword := range bytes.Fields(b) {
bword := bytes.Trim(bword, ".,-~?!\"'`;:()<>[]{}\\|/=_+*&^%$#@")
if len(bword) > 0 {
word := string(bword)
dl := index[word]
for _, d := range dl {
if d == x {
continue wordLoop
}
}
index[word] = append(dl, x)
}
}
}
return true
}
func ui() {
fmt.Println(len(index), "words indexed in", len(indexed), "files")
fmt.Println("enter single words to search for")
fmt.Println("enter a blank line when done")
var word string
for {
fmt.Print("search word: ")
wc, _ := fmt.Scanln(&word)
if wc == 0 {
return
}
switch dl := index[word]; len(dl) {
case 0:
fmt.Println("no match")
case 1:
fmt.Println("one match:")
fmt.Println(" ", indexed[dl[0]].file, indexed[dl[0]].title)
default:
fmt.Println(len(dl), "matches:")
for _, d := range dl {
fmt.Println(" ", indexed[d].file, indexed[d].title)
}
}
}
}</lang> Session:
8447 words indexed in 11 files
enter single words to search for
enter a blank line when done
search word: dog
no match
search word: cat
one match:
docs/pg28554.txt Beyond Lies the Wub
search word: robot
6 matches:
docs/pg32032.txt Second Variety
docs/pg32522.txt Mr. Spaceship
docs/pg32832.txt Piper in the Woods
docs/pg28698.txt The Crystal Crypt
docs/pg28767.txt The Defenders
docs/pg32154.txt The Variable Man
Haskell
<lang haskell>import Control.Monad import Data.Char (isAlpha, toLower) import qualified Data.Map as M import qualified Data.IntSet as S import System.Environment (getArgs)
main = do
(files, _ : q) <- liftM (break (== "--")) getArgs buildII files >>= mapM_ putStrLn . queryII q
data IIndex = IIndex
[FilePath] -- Files in the index (M.Map String S.IntSet) -- Maps word to indices of the list deriving Show
buildII :: [FilePath] -> IO IIndex buildII files =
liftM (IIndex files . foldl f M.empty . zip [0..]) $
mapM readFile files
where f m (i, s) =
foldl g m $ map (lowercase . filter isAlpha) $ words s
where g m word = M.insertWith S.union word (S.singleton i) m
queryII :: [String] -> IIndex -> [FilePath] queryII q (IIndex files m) =
map (files !!) $ S.toList $ intersections $ map (\word -> M.findWithDefault S.empty (lowercase word) m) q
intersections [] = S.empty intersections xs = foldl1 S.intersection xs
lowercase = map toLower</lang>
An example of use, assuming the program is named iindex and there exist files t0, t1, and t2 with contents "It is what it is.", "What is it?", and "It is a banana.":
$ iindex t0 t1 t2 -- what is it t0 t1
J
This just implements the required spec, with a simplistic definition for what a word is, and with no support for stop words, nor for phrase searching.
<lang J>require'files regex strings'
rxutf8 0 NB. support latin1 searches for this example, instead of utf8 files=:words=:buckets=: wordre=: rxcomp '[\w]+' parse=: ,@:rxfrom~ wordre&rxmatches
invert=: verb define
files=: files,todo=. ~.y-.files >invert1 each todo
)
invert1=: verb define
file=. files i.<y
words=: ~.words,contents=. ~.parse tolower fread jpath y
ind=. words i. contents
buckets=: buckets,(1+words -&# buckets)#a:
#buckets=: (file,~each ind{buckets) ind}buckets
)
search=: verb define
hits=. buckets{~words i.~.parse tolower y
files {~ >([-.-.)each/hits
)</lang>
Example use:
<lang J> invert '~help/primer/cut.htm';'~help/primer/end.htm';'~help/primer/gui.htm'
>search 'finally learning'
~help/primer/end.htm ~help/primer/gui.htm
>search 'argument'
~help/primer/cut.htm ~help/primer/gui.htm
>search 'around'
~help/primer/gui.htm</lang>
OCaml
We store the inverted index data in the file "data.inv" using the sexplib library, so we compile with:
ocamlc -c \
-pp "camlp4o -I `ocamlc -where`/type-conv \
-I `ocamlc -where`/sexplib \
pa_type_conv.cmo pa_sexp_conv.cmo" \
unix.cma bigarray.cma nums.cma -I +sexplib sexplib.cma str.cma \
inv.ml
ocamlc -o inv.byte unix.cma bigarray.cma nums.cma -I +sexplib sexplib.cma str.cma inv.cmo
<lang ocaml>TYPE_CONV_PATH "Inverted_index"
type files = string array with sexp type inverted_index = (string * int list) list with sexp
type t = files * inverted_index with sexp
open Sexplib
let data_file = "data.inv" let data_path = Filename.concat Filename.temp_dir_name data_file
let get_inv_index() =
if Sys.file_exists data_path then t_of_sexp(Sexp.load_sexp data_path) else ([| |], [])
let load_file f =
let ic = open_in f in let n = in_channel_length ic in let s = String.create n in really_input ic s 0 n; close_in ic; (s)
let array_push ar v =
let len = Array.length ar in Array.init (succ len) (fun i -> if i < len then Array.unsafe_get ar i else v), len
let uniq lst =
let h = Hashtbl.create (List.length lst) in List.iter (fun x -> Hashtbl.replace h x ()) lst; Hashtbl.fold (fun x () xs -> x :: xs) h []
let combine words i inv_index =
let h = Hashtbl.create (List.length inv_index) in
List.iter (fun (w, from) -> Hashtbl.replace h w from) inv_index;
List.iter (fun w ->
if Hashtbl.mem h w
then begin
let from = Hashtbl.find h w in
Hashtbl.replace h w (i::from)
end else
Hashtbl.add h w [i]
) words;
Hashtbl.fold (fun w from acc -> (w, from) :: acc) h []
let words_of_file in_file =
let str = load_file in_file in let words = Str.split (Str.regexp "[ \r\n\t,;.?!:'/\034()]") str in let words = uniq words in (words)
let index_file in_file =
let words = words_of_file in_file in let files, inv_index = get_inv_index() in let files, i = array_push files in_file in let inv_index = combine words i inv_index in let se = sexp_of_t (files, inv_index) in Sexp.save data_path se
let search_word word =
let files, inv_index = get_inv_index() in try let is_in = List.assoc word inv_index in List.iter (fun i -> print_endline files.(i)) is_in with Not_found -> print_endline "# Not Found"
let usage() =
Printf.printf "Usage: %s \ --index-file <file.txt> / \ --search-word <some-word>\n%!" Sys.argv.(0); exit 1
let () =
let cmd, arg = try (Sys.argv.(1), Sys.argv.(2)) with _ -> usage() in match cmd, arg with | "--index-file", in_file -> index_file in_file | "--search-word", word -> search_word word | _ -> usage()</lang>
Perl
<lang perl>use Set::Object 'set';
- given an array of files, returns the index
sub createindex {
my @files = @_;
my %iindex;
foreach my $file (@files)
{
open(F, "<", $file) or die "Can't read file $file: $!"; while(<F>) {
s/\A\W+//;
foreach my $w (map {lc} grep {length() >= 3} split /\W+/) { if ( exists($iindex{$w}) ) { $iindex{$w}->insert($file); } else { $iindex{$w} = set($file); } } } close(F);
} return %iindex;
}
- given an index, search for words
sub search_words_with_index {
my %idx = %{shift()};
my @words = @_;
my $res = set();
foreach my $w (map {lc} @words)
{
$w =~ s/\W+//g; # strip non-words chars
length $w < 3 and next;
exists $idx{$w} or return set();
$res = $res->is_null
? set(@{$idx{$w}})
: $res * $idx{$w}; # set intersection
}
return @$res;
}
- TESTING
- USAGE: invidx.pl the,list,of,words file1 file2 .. fileN
my @searchwords = split /,/, shift;
- first arg is a comma-separated list of words to search for
print "$_\n"
foreach search_words_with_index({createindex(@ARGV)}, @searchwords);</lang>
PicoLisp
Assuming three files "file1", "file2" and "file3":
$ cat file1 it is what it is $ cat file2 what is it $ cat file3 it is a banana
we can read them into a binary tree in the global variable '*MyIndex' <lang PicoLisp>(off *MyIndex)
(use Word
(for File '("file1" "file2" "file3")
(in File
(while (skip)
(if (idx '*MyIndex (setq Word (till " ^I^J^M" T)) T)
(push1 (car @) File)
(set Word (cons File)) ) ) ) ) )
(de searchFor @
(apply sect
(extract
'((Word) (val (car (idx '*MyIndex Word))))
(rest) ) ) )</lang>
Output:
: (searchFor "what" "is" "it")
-> ("file2" "file1")
: (searchFor "a" "banana")
-> ("file3")
: (searchFor "it" "is")
-> ("file3" "file2" "file1")
Python
Simple inverted index
First the simple inverted index from here together with an implementation of a search for (multiple) terms from that index. <lang python> This implements: http://en.wikipedia.org/wiki/Inverted_index of 28/07/10
from pprint import pprint as pp from glob import glob try: reduce except: from functools import reduce try: raw_input except: raw_input = input
def parsetexts(fileglob='InvertedIndex/T*.txt'):
texts, words = {}, set()
for txtfile in glob(fileglob):
with open(txtfile, 'r') as f:
txt = f.read().split()
words |= set(txt)
texts[txtfile.split('\\')[-1]] = txt
return texts, words
def termsearch(terms): # Searches simple inverted index
return reduce(set.intersection,
(invindex[term] for term in terms),
set(texts.keys()))
texts, words = parsetexts() print('\nTexts') pp(texts) print('\nWords') pp(sorted(words))
invindex = {word:set(txt
for txt, wrds in texts.items() if word in wrds)
for word in words}
print('\nInverted Index') pp({k:sorted(v) for k,v in invindex.items()})
terms = ["what", "is", "it"] print('\nTerm Search for: ' + repr(terms)) pp(sorted(termsearch(terms)))</lang>
Sample Output
Texts
{'T0.txt': ['it', 'is', 'what', 'it', 'is'],
'T1.txt': ['what', 'is', 'it'],
'T2.txt': ['it', 'is', 'a', 'banana']}
Words
['a', 'banana', 'is', 'it', 'what']
Inverted Index
{'a': ['T2.txt'],
'banana': ['T2.txt'],
'is': ['T0.txt', 'T1.txt', 'T2.txt'],
'it': ['T0.txt', 'T1.txt', 'T2.txt'],
'what': ['T0.txt', 'T1.txt']}
Term Search for: ['what', 'is', 'it']
['T0.txt', 'T1.txt']
Full inverted index
There is a re-write of the termsearch function to work off this type of index, as well as a new phrasesearch function
The phrasesearch function will return multiple matches in a text, and goes on to show how this can be used to pick the text with most matches.
It is assumed that the following code is added to the end of the code for the simple case above and so shares its file opening and parsing results <lang python>from collections import Counter
def termsearch(terms): # Searches full inverted index
if not set(terms).issubset(words):
return set()
return reduce(set.intersection,
(set(x[0] for x in txtindx)
for term, txtindx in finvindex.items()
if term in terms),
set(texts.keys()) )
def phrasesearch(phrase):
wordsinphrase = phrase.strip().strip('"').split()
if not set(wordsinphrase).issubset(words):
return set()
#firstword, *otherwords = wordsinphrase # Only Python 3
firstword, otherwords = wordsinphrase[0], wordsinphrase[1:]
found = []
for txt in termsearch(wordsinphrase):
# Possible text files
for firstindx in (indx for t,indx in finvindex[firstword]
if t == txt):
# Over all positions of the first word of the phrase in this txt
if all( (txt, firstindx+1 + otherindx) in finvindex[otherword]
for otherindx, otherword in enumerate(otherwords) ):
found.append(txt)
return found
finvindex = {word:set((txt, wrdindx)
for txt, wrds in texts.items()
for wrdindx in (i for i,w in enumerate(wrds) if word==w)
if word in wrds)
for word in words}
print('\nFull Inverted Index') pp({k:sorted(v) for k,v in finvindex.items()})
print('\nTerm Search on full inverted index for: ' + repr(terms)) pp(sorted(termsearch(terms)))
phrase = '"what is it"' print('\nPhrase Search for: ' + phrase) print(phrasesearch(phrase))
- Show multiple match capability
phrase = '"it is"' print('\nPhrase Search for: ' + phrase) ans = phrasesearch(phrase) print(ans) ans = Counter(ans) print(' The phrase is found most commonly in text: ' + repr(ans.most_common(1)[0][0]))</lang>
Sample Output
Full Inverted Index
{'a': [('T2.txt', 2)],
'banana': [('T2.txt', 3)],
'is': [('T0.txt', 1), ('T0.txt', 4), ('T1.txt', 1), ('T2.txt', 1)],
'it': [('T0.txt', 0), ('T0.txt', 3), ('T1.txt', 2), ('T2.txt', 0)],
'what': [('T0.txt', 2), ('T1.txt', 0)]}
Term Search on full inverted index for: ['what', 'is', 'it']
['T0.txt', 'T1.txt']
Phrase Search for: "what is it"
['T1.txt']
Phrase Search for: "it is"
['T0.txt', 'T0.txt', 'T2.txt']
The phrase is found most commonly in text: 'T0.txt'
REXX
Note: In this algorithm, word indices start at 1. <lang rexx> /*REXX program illustrates building a simple inverted index & word find.*/
@.= /*dictionary of words (so far).*/ != /*a list of found words (so far).*/
call invertI 0,'BURMA0.TXT' /*read file 0 ... */ call invertI 1,'BURMA1.TXT' /* " " 1 ... */ call invertI 2,'BURMA2.TXT' /* " " 2 ... */ call invertI 3,'BURMA3.TXT' /* " " 3 ... */ call invertI 4,'BURMA4.TXT' /* " " 4 ... */ call invertI 5,'BURMA5.TXT' /* " " 5 ... */ call invertI 6,'BURMA6.TXT' /* " " 6 ... */ call invertI 7,'BURMA7.TXT' /* " " 7 ... */ call invertI 8,'BURMA8.TXT' /* " " 8 ... */ call invertI 9,'BURMA9.TXT' /* " " 9 ... */
call findAword 'does' /*find a word. */ call findAword '60' /*find another word. */ call findAword "don't" /*and find another word. */ call findAword "burma-shave" /*and find yet another word. */ exit /*enough of this, I'm tired. */
/*─────────────────────────────────────FINDAWORD subroutine─────────────*/ findAword: procedure expose @. /*get A word, and uppercase it. */ parse arg ox; arg x /*OX= word; X= uppercase version*/ _=@.x oxo='───'ox"───"
if _== then do
say 'word' oxo "not found."
return 0
end
_@=_ /*save _, pass it back to invoker*/ say 'word' oxo "found in:"
do until _== parse var _ f w _ say ' file='f ' word='w end
return _@
/*─────────────────────────────────────INVERTI subroutine───────────────*/
invertI: procedure expose @. !; parse arg #,fn /*file#, filename*/
call lineout fn /*close the file, just in case. */
w=0 /*number of words so far. */
do while lines(fn)\==0 /*read the entire file. */ _=linein(fn) /*read the file, 1 line at a time*/ _=space(_); if _= then iterate /*if blank record, then ignore it*/
say 'file' #",record="_ /*echo a record, just to be verbose.*/
upper _ /*make it case insensative. */
do until _== /*pick off words until done. */ parse var _ xxx _ /*pick off a word. */ xxx=stripper(xxx) /*go and strip off ending punct. */ if xxx= then iterate /*is the word now blank (null) ? */ w=w+1 /*bump the word counter. */ @.xxx=@.xxx # w if wordpos(xxx,!)==0 then !=! xxx /*add to THE list of words found.*/ end
end
call lineout fn /*close the file, just to be neat*/ return w
/*─────────────────────────────────────STRIPPER subroutine──────────────*/
stripper: procedure; parse arg q /*remove punctuation at word-end.*/
@punctuation='.,:;?¿!¡' /*serveral punctuation marks. */
do j=1 for length(@punctuation) q=strip(q,'T',substr(@punctuation,j,1)) end
return q </lang> Output:
file 0,record=Rip a fender
file 0,record=off your car
file 0,record=send it in
file 0,record=for a half-pound jar
file 0,record=Burma-shave
file 1,record=A peach
file 1,record=looks good
file 1,record=with lots of fuzz
file 1,record=but a man's no peach
file 1,record=and never was
file 1,record=Burma-shave
file 2,record=Does your husband
file 2,record=misbehave
file 2,record=grunt and grumble
file 2,record=rant and rave ?
file 2,record=shoot the brute some
file 2,record=Burma-shave
file 3,record=Don't take a curve
file 3,record=at 60 per
file 3,record=we hate to lose
file 3,record=a customer
file 3,record=Burma-shave
file 4,record=Every shaver
file 4,record=now can snore
file 4,record=six more minutes
file 4,record=than before
file 4,record=by using
file 4,record=Burma-shave
file 5,record=He played
file 5,record=a sax
file 5,record=had no B.O.
file 5,record=but his whiskers scratched
file 5,record=so they let him go
file 5,record=Burma-shave
file 6,record=Henry the Eighth
file 6,record=Prince of Friskers
file 6,record=lost five wives
file 6,record=but kept his whiskers
file 6,record=Burma-shave
file 7,record=Listen, birds
file 7,record=those signs cost
file 7,record=money
file 7,record=so roost a while but
file 7,record=don't get funny
file 7,record=Burma-shave
file 8,record=My man
file 8,record=won't shave
file 8,record=sez Hazel Huz
file 8,record=but I should worry
file 8,record=Dora's does
file 8,record=Burma-shave
file 9,record=Past schoolhouses
file 9,record=take it slow
file 9,record=let the little
file 9,record=shavers
file 9,record=grow
file 9,record=Burma-shave
word ---does--- found in:
file=2 word=1
file=8 word=13
word ---60--- found in:
file=3 word=6
word ---don't--- found in:
file=3 word=1
file=7 word=12
word ---burma-shave--- found in:
file=0 word=14
file=1 word=17
file=2 word=15
file=3 word=14
file=4 word=13
file=5 word=17
file=6 word=14
file=7 word=15
file=8 word=14
file=9 word=11
Ruby
I broke this into two parts, storing the index as a file on disk to better represent how this might actually be used in practice. The indexmerge part will create or update the index data file with any files given on the command line, and then indexsearch will use the data file to search for any terms listed on the command line. The example is based on http://en.wikipedia.org/wiki/Inverted_index of 2010/09/10.
indexmerge.rb <lang ruby>if File.exist? "index.dat"
@data = Marshal.load open("index.dat")
else
@data = {}
end
- Let's give the string class the ability to tokenize itsself into lowercase
- words with no punctuation.
class String
def index_sanitize
self.split.collect do |token|
token.downcase.gsub(/\W/, )
end
end
end
- Just implementing a simple inverted index here.
ARGV.each do |filename|
open filename do |file|
file.read.index_sanitize.each do |word|
@data[word] ||= []
@data[word] << filename unless @data[word].include? filename
end
end
end
open("index.dat", "w") do |index|
index.write Marshal.dump(@data)
end</lang>
indexsearch.rb <lang ruby>if File.exist? "index.dat"
@data = Marshal.load open("index.dat")
else
raise "The index data file could not be located."
end
class String
def index_sanitize
self.split.collect do |token|
token.downcase.gsub(/\W/, )
end
end
end
- Take anything passed in on the command line in any form and break it
- down the same way we did when making the index.
ARGV.join(' ').index_sanitize.each do |word|
@result ||= @data[word] @result &= @data[word]
end
p @result</lang>
Output
> ./indexmerge.rb file1 > ./indexmerge.rb file2 file3 > ./indexsearch.rb what is it ["file1", "file2"] > ./indexsearch.rb "a banana" ["file3"] > ./indexsearch.rb It iS\! ["file1", "file2", "file3"]
Tcl
<lang tcl>package require Tcl 8.5 proc wordsInString str {
# We define "words" to be "maximal sequences of 'word' characters".
# The other possible definition is to use 'non-space' characters.
regexp -all -inline {\w+} $str
}
- Adds a document to the index. The index is a map from words to a map
- from filenames to lists of word locations.
proc addDocumentToIndex {filename} {
global index set f [open $filename] set data [read $f] close $f
set i 0
array set localidx {}
foreach word [wordsInString $data] {
lappend localidx($word) $i incr i
}
# Transcribe into global index
foreach {word places} [array get localidx] {
dict set index($word) $filename $places
}
}
- How to use the index to find files containing a word
proc findFilesForWord {word} {
global index
if {[info exists index($word)]} {
return [dict keys $index($word)]
}
}
- How to use the index to find files containing all words from a list.
- Note that this does not use the locations within the file.
proc findFilesWithAllWords {words} {
set files [findFilesForWord [lindex $words 0]]
foreach w [lrange $words 1 end] {
set wf [findFilesForWord $w] set newfiles {} foreach f $files { if {$f in $wf} {lappend newfiles $f} } set files $newfiles
} return $files
}
- How to use the index to find a sequence of words in a file.
proc findFilesWithWordSequence {words} {
global index
set files {}
foreach w $words {
if {![info exist index($w)]} { return }
}
dict for {file places} $index([lindex $words 0]) {
if {$file in $files} continue foreach start $places { set gotStart 1 foreach w [lrange $words 1 end] { incr start set gotNext 0 foreach {f ps} $index($w) { if {$f ne $file} continue foreach p $ps { if {$p == $start} { set gotNext 1 break } } if {$gotNext} break } if {!$gotNext} { set gotStart 0 break } } if {$gotStart} { lappend files $file break } }
} return $files
}</lang> For the GUI: <lang tcl>package require Tk pack [labelframe .files -text Files] -side left -fill y pack [listbox .files.list -listvariable files] pack [button .files.add -command AddFile -text "Add File to Index"] pack [labelframe .found -text Found] -side right -fill y pack [listbox .found.list -listvariable found] -fill x pack [entry .found.entry -textvariable terms] -fill x pack [button .found.findAll -command FindAll \ -text "Find File with All"] -side left pack [button .found.findSeq -command FindSeq \ -text "Find File with Sequence"] -side right
- The actions invoked by various GUI buttons
proc AddFile {} {
global files
set f [tk_getOpenFile]
if {$f ne ""} {
addDocumentToIndex $f lappend files $f
}
} proc FindAll {} {
global found terms
set words [wordsInString $terms]
set fs [findFilesWithAllWords $words]
lappend found "Searching for files with all $terms" {*}$fs \
"---------------------" } proc FindSeq {} {
global found terms
set words [wordsInString $terms]
set fs [findFilesWithWordSequence $words]
lappend found "Searching for files with \"$terms\"" {*}$fs \
"---------------------" }</lang>
TUSCRIPT
<lang tuscript> $$ MODE TUSCRIPT
files="file1'file2'file3" LOOP file=files ERROR/STOP CREATE (file,seq-o,-std-) ENDLOOP
content1="it is what it is" content2="what is it" content3="it is a banana"
FILE/ERASE "file1" = content1 FILE/ERASE "file2" = content2 FILE/ERASE "file3" = content3
ASK "search for": search="" IF (search=="") STOP
BUILD R_TABLE/USER/AND search = * DATA {search}
LOOP/CLEAR file=files
ACCESS q: READ/RECORDS $file s.z/u,content,count LOOP COUNT/NEXT/EXIT q (-; search;-;-) IF (count!=0) files=APPEND (files," ",file) ENDLOOP ENDACCESs q
ENDLOOP PRINT "-> ",files </lang> Output:
search for >what is it -> file1 file2 search for >banana -> file3 search for >it is -> file1 file2 file3
UNIX Shell
Associative array
<lang bash>#!/bin/ksh
typeset -A INDEX
function index {
typeset num=0
for file in "$@"; do
tr -s '[:punct:]' ' ' < "$file" | while read line; do
for token in $line; do
INDEX[$token][$num]=$file
done
done
((++num))
done
}
function search {
for token in "$@"; do
for file in "${INDEX[$token][@]}"; do
echo "$file"
done
done | sort | uniq -c | while read count file; do
(( count == $# )) && echo $file
done
}</lang>
Example use: <lang korn>index *.txt search hello world </lang>
Directory on filesystem
The following is an attempt (not yet complete) to port the above script to pdksh, and perhaps other Bourne-compatible shells.
- TODO Fill in "search.sh".
- Add note about slowness.
<lang bash>#!/bin/sh
- index.sh - create an inverted index
unset IFS
- ${INDEX:=index}
- Prohibit '\n' in filenames (because '\n' is
- the record separator for $INDEX/all.tab).
for file in "$@"; do # Use printf(1), not echo, because "$file" might start with # a hyphen and become an option to echo. test 0 -eq $(printf %s "$file" | wc -l) || { printf '%s\n' "$file: newline in filename" >&2 exit 1 } done
- Make a new directory for the index, or else
- exit with the error message from mkdir(1).
mkdir "$INDEX" || exit $?
fi=1 for file in "$@"; do printf %s "Indexing $file." >&2
# all.tab maps $fi => $file echo "$fi $file" >> "$INDEX/all.tab"
# Use punctuation ([:punct:]) and whitespace (IFS) # to split tokens. ti=1 tr -s '[:punct:]' ' ' < "$file" | while read line; do for token in $line; do # Index token by position ($fi, $ti). Ignore # error from mkdir(1) if directory exists. mkdir "$INDEX/$token" 2>/dev/null echo $ti >> "$INDEX/$token/$fi" : $((ti += 1))
# Show progress. Print a dot per 1000 tokens. case "$ti" in *000) printf . esac done done
echo >&2 : $((fi += 1)) done</lang>
<lang bash>#!/bin/sh
- search.sh - search an inverted index
unset IFS
- ${INDEX:=index}
want=sequence while getopts aos name; do case "$name" in a) want=all;; o) want=one;; s) want=sequence;; *) exit 2;; esac done shift $((OPTIND - 1))
all() { echo "TODO" exit 2 }
one() { echo "TODO" exit 2 }
sequence() { echo "TODO" exit 2 }
$want "$@"</lang>