N-grams

From Rosetta Code
N-grams is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

An N-gram is a sequence of N contiguous elements of a given text. Although N-grams refer sometimes to words or syllables, in this task we will consider only sequences of characters. The task consists in, given a text and an integer size of the desired N-grams, find all the different contiguous sequences of N characters, together with the number of times they appear in the text. For example, the 2-grams of the text "Live and let live" are: 

 "LI" - 2
 "IV" - 2
 "VE" - 2
 " L" - 2
 "E " - 1
 " A" - 1
 "AN" - 1
 "ND" - 1
 "D " - 1
 "LE" - 1
 "ET" - 1
 "T " - 1

Note that space and other non-alphanumeric characters are taken into account.


See also


Arturo[edit]

ngrams: function [s :string n :integer][
    0..sub size s n | map 'i -> slice upper s i i+n-1
                    | tally
]

loop [2 3 4] 'n [
    print ~"|n|-grams:"
    loop ngrams "Live and let live" n [k v] -> print [~{"|k|"} v]
    print ""
]
Output:
2-grams:
"LI" 2 
"IV" 2 
"VE" 2 
"E " 1 
" A" 1 
"AN" 1 
"ND" 1 
"D " 1 
" L" 2 
"LE" 1 
"ET" 1 
"T " 1 

3-grams:
"LIV" 2 
"IVE" 2 
"VE " 1 
"E A" 1 
" AN" 1 
"AND" 1 
"ND " 1 
"D L" 1 
" LE" 1 
"LET" 1 
"ET " 1 
"T L" 1 
" LI" 1 

4-grams:
"LIVE" 2 
"IVE " 1 
"VE A" 1 
"E AN" 1 
" AND" 1 
"AND " 1 
"ND L" 1 
"D LE" 1 
" LET" 1 
"LET " 1 
"ET L" 1 
"T LI" 1 
" LIV" 1

C[edit]

#include <stdio.h>
#include <stdbool.h>
#include <ctype.h>
#include <string.h>

#define MAX_N 4
#define MAX_NGRAMS 20

typedef struct {
    char str[MAX_N+1];
    int freq;
} ngram;

void *strUpper(char *s) {
    while (*s) {
        *s = toupper(*s);
        s++;
    }
}

void ngrams(int n, char *text) {
    int i, j, count = 0;
    size_t len = strlen(text);
    bool found;
    char temp[MAX_N+1] = {'\0'};
    ngram ng, ngrams[MAX_NGRAMS];
    char s[len+1];
    strcpy(s, text);
    strUpper(s);
    for (i = 0; i <= len-n; ++i) {
        strncpy(temp, s + i, n);
        found = false;
        for (j = 0; j < count; ++j) {    
            if (!strcmp(ngrams[j].str, temp)) {
                ngrams[j].freq++;
                found = true;
                break;
            }
        }
        if (!found) {
            strncpy(ng.str, temp, n);
            ng.freq = 1;
            ngrams[count++] = ng;
        }
    }
    for (i = 0; i < count; ++i) {
        printf("(\"%s\": %d)  ", ngrams[i].str, ngrams[i].freq);
        if (!((i+1)%5)) printf("\n");
    }
    printf("\n\n");
}

int main() {
    int n;
    char *text = "Live and let live";
    for (n = 2; n <= MAX_N; ++n) {
        printf("All %d-grams of '%s' and their frequencies:\n", n, text);
        ngrams(n, text);
    }
    return 0;
}
Output:
All 2-grams of 'Live and let live' and their frequencies:
("LI": 2)  ("IV": 2)  ("VE": 2)  ("E ": 1)  (" A": 1)  
("AN": 1)  ("ND": 1)  ("D ": 1)  (" L": 2)  ("LE": 1)  
("ET": 1)  ("T ": 1)  

All 3-grams of 'Live and let live' and their frequencies:
("LIV": 2)  ("IVE": 2)  ("VE ": 1)  ("E A": 1)  (" AN": 1)  
("AND": 1)  ("ND ": 1)  ("D L": 1)  (" LE": 1)  ("LET": 1)  
("ET ": 1)  ("T L": 1)  (" LI": 1)  

All 4-grams of 'Live and let live' and their frequencies:
("LIVE": 2)  ("IVE ": 1)  ("VE A": 1)  ("E AN": 1)  (" AND": 1)  
("AND ": 1)  ("ND L": 1)  ("D LE": 1)  (" LET": 1)  ("LET ": 1)  
("ET L": 1)  ("T LI": 1)  (" LIV": 1)

Common Lisp[edit]

A hash table is used to store and retrieve the n-grams fast. 

(defun n-grams (text n)
"Return a list of all the N-grams of length n in the text, together with their frequency"
	(let* (res (*ht-n-grams* (make-hash-table :test 'equal)) )
		(loop for i from 0 to (- (length text) n) do
			(let* ((n-gram (string-upcase (subseq text i (+ i n))))
			       (freq (gethash n-gram *ht-n-grams*)))
		  		(setf (gethash n-gram *ht-n-grams*) (if (null freq) 1 (1+ freq))) ))
			(maphash #'(lambda (key val)
									(push (cons key val) res) )
				*ht-n-grams* )
			(sort res #'> :key #'cdr) ))
Output:
> (n-grams "Live and let live" 2)

(("LI" . 2) ("IV" . 2) ("VE" . 2) (" L" . 2) ("E " . 1) (" A" . 1) ("AN" . 1)
 ("ND" . 1) ("D " . 1) ("LE" . 1) ("ET" . 1) ("T " . 1))

Factor[edit]

Works with: Factor version 0.99 2022-04-03
USING: ascii grouping kernel math.statistics prettyprint ;

: n-grams ( str n -- assoc ) [ >upper ] dip clump histogram ;

"Live and let live" 2 n-grams .
Output:
H{
    { "ET" 1 }
    { "IV" 2 }
    { "T " 1 }
    { " A" 1 }
    { "VE" 2 }
    { "LI" 2 }
    { "E " 1 }
    { "D " 1 }
    { " L" 2 }
    { "ND" 1 }
    { "LE" 1 }
    { "AN" 1 }
}

jq[edit]

Works with jq and gojq, that is, the C and Go implementations of jq. 

# Generic "bag of words" utility:
def bow(stream): 
  reduce stream as $word ({}; .[($word|tostring)] += 1);

# The ngrams as a bow
def ngrams($n):
  ascii_upcase as $text
  | bow( range(0;$text|1+ length - $n) as $i | $text[$i:$i+$n]);

# The task
# Sort by increasing frequency, then by lexicographical order
def ngrams($text; $n):
  ($text|ngrams($n)) as $ngrams
  | "\nAll \($n)-grams of '\($text)' and their frequencies:",
    ($ngrams|to_entries|sort_by(.value,.key)[] | "\(.key): \(.value)" ) ;

ngrams("Live and let live"; 2,3,4)
Output:

All 2-grams of 'Live and let live' and their frequencies:
 A: 1
AN: 1
D : 1
E : 1
ET: 1
LE: 1
ND: 1
T : 1
 L: 2
IV: 2
LI: 2
VE: 2

All 3-grams of 'Live and let live' and their frequencies:
 AN: 1
 LE: 1
 LI: 1
AND: 1
D L: 1
E A: 1
ET : 1
LET: 1
ND : 1
T L: 1
VE : 1
IVE: 2
LIV: 2

All 4-grams of 'Live and let live' and their frequencies:
 AND: 1
 LET: 1
 LIV: 1
AND : 1
D LE: 1
E AN: 1
ET L: 1
IVE : 1
LET : 1
ND L: 1
T LI: 1
VE A: 1
LIVE: 2

Julia[edit]

function ngrams(str::AbstractString, n; uppercaseinput = true)
    s = uppercaseinput ? uppercase(str) : str
    unique([(ng, count(ng, s)) for ng in [SubString(s, i:i+n-1) for i=1:length(s)-n+1]])
end

function eightcolumns(arr)
    for (i, elem) in pairs(arr)
        print(lpad(elem, 10), i % 8 == 0 ? "\n" : "")
    end
    println("\n")
end
        
const s = "Live and let live"

ngrams(s, 1) |> eightcolumns
ngrams(s, 2) |> eightcolumns
ngrams(s, 2, uppercaseinput = false) |> eightcolumns
Output:
  ("L", 3)  ("I", 2)  ("V", 2)  ("E", 3)  (" ", 3)  ("A", 1)  ("N", 1)  ("D", 1)
  ("T", 1)

 ("LI", 2) ("IV", 2) ("VE", 2) ("E ", 1) (" A", 1) ("AN", 1) ("ND", 1) ("D ", 1)
 (" L", 2) ("LE", 1) ("ET", 1) ("T ", 1)

 ("Li", 1) ("iv", 2) ("ve", 2) ("e ", 1) (" a", 1) ("an", 1) ("nd", 1) ("d ", 1)
 (" l", 2) ("le", 1) ("et", 1) ("t ", 1) ("li", 1)

Nim[edit]

import std/[strutils, tables]

type NGrams = CountTable[string]

func ngrams(text: string; n: Positive): NGrams =
  for i in 0..(text.len - n):
    result.inc(text[i..<(i + n)].toLowerAscii)

const Text = "Live and let live"

for n in 2..4:
  echo n, "-grams:"
  var ng = Text.ngrams(n)
  ng.sort()               # To display n-grams with higher score first.
  for key, count in ng:
    echo "“$1”: $2".format(key, count)
  echo()

2-grams:
“ve”: 2
“li”: 2
“iv”: 2
“ l”: 2
“d ”: 1
“et”: 1
“t ”: 1
“an”: 1
“nd”: 1
“e ”: 1
“le”: 1
“ a”: 1

3-grams:
“ive”: 2
“liv”: 2
“ le”: 1
“nd ”: 1
“and”: 1
“et ”: 1
“ve ”: 1
“t l”: 1
“ an”: 1
“d l”: 1
“e a”: 1
“let”: 1
“ li”: 1

4-grams:
“live”: 2
“ liv”: 1
“ and”: 1
“e an”: 1
“ let”: 1
“and ”: 1
“d le”: 1
“t li”: 1
“nd l”: 1
“et l”: 1
“ive ”: 1
“let ”: 1
“ve a”: 1

Perl[edit]

use v5.36;

sub n_gram ($n, $line) {
    my %N;
    map { $N{substr lc($line),$_,$n}++ } 0..length($line)-$n;
    %N
}

my %bi_grams = n_gram 2, 'Live and let live';
say qq|'$_' - $bi_grams{$_}| for sort keys %bi_grams;

say '';

my %tri_grams = n_gram 3, 'Live and let live';
say qq|'$_' - $tri_grams{$_}| for sort keys %tri_grams;
Output:
' a' - 1
' l' - 2
'an' - 1
'd ' - 1
'e ' - 1
'et' - 1
'iv' - 2
'le' - 1
'li' - 2
'nd' - 1
't ' - 1
've' - 2

' an' - 1
' le' - 1
' li' - 1
'and' - 1
'd l' - 1
'e a' - 1
'et ' - 1
'ive' - 2
'let' - 1
'liv' - 2
'nd ' - 1
't l' - 1
've ' - 1

Phix[edit]

A dictionary is used to find the index of already-seen n-grams, even though a simpler find() would be good enough for this task.
I have replicated most orderings found on this page, the task description order corresponds to orig/freq,
and jq is alpha/freq with high last, but there is no equivalent for the Factor or Raku orderings here ;-). 

with javascript_semantics
function n_grams(integer len, string txt, sequence orders)
    sequence ng = {}, ngc = {}
    integer d = new_dict()
    txt = upper(txt)
    for i=1 to length(txt)-len+1 do
        string tn = txt[i..i+len-1]
        integer ndx = getdd(tn,0,d)
        if ndx=0 then
            ng = append(ng,tn)
            ngc = append(ngc,1)
            ndx = length(ng)
            setd(tn,ndx,d)
        else
            ngc[ndx] += 1
        end if
    end for
    destroy_dict(d)
    integer l = length(ng)
    sequence ares = columnize({ng,ngc,tagset(l)}),
              res = {}
    for c in orders do
        if c="original" then -- original/first found order
            res = append(res,ares)
        elsif c="orig/freq" then -- "" but higher freq first
            res = append(res,sort_columns(ares,{-2,3}))
        elsif c="alphabetic" then -- alphabetical order
            res = append(res,sort(deep_copy(ares)))
        elsif c="alpha/freq" then -- "" but higher freq first
            res = append(res,sort_columns(ares,{-2,1}))
        else
            ?9/0 -- (unknown ordering requested)
        end if
    end for
    return res
end function

constant src = "Live and let live",
         orders = {"original","orig/freq",
                 "alphabetic","alpha/freq"}
printf(1,"For \"%s\":\n",src)
for l=2 to 4 do
    sequence res = n_grams(l,src,orders)
    string count = ordinal(length(res[1]),true)
    printf(1,"There are %s unique %d-grams:\n",{count,l})
    for i,r in res do
        printf(1,"%12s: %s\n",{orders[i],join(r,", ",fmt:="%s %d")})
    end for
end for
Output:
For "Live and let live":
There are twelve unique 2-grams:
    original: LI 2, IV 2, VE 2, E  1,  A 1, AN 1, ND 1, D  1,  L 2, LE 1, ET 1, T  1
   orig/freq: LI 2, IV 2, VE 2,  L 2, E  1,  A 1, AN 1, ND 1, D  1, LE 1, ET 1, T  1
  alphabetic:  A 1,  L 2, AN 1, D  1, E  1, ET 1, IV 2, LE 1, LI 2, ND 1, T  1, VE 2
  alpha/freq:  L 2, IV 2, LI 2, VE 2,  A 1, AN 1, D  1, E  1, ET 1, LE 1, ND 1, T  1
There are thirteen unique 3-grams:
    original: LIV 2, IVE 2, VE  1, E A 1,  AN 1, AND 1, ND  1, D L 1,  LE 1, LET 1, ET  1, T L 1,  LI 1
   orig/freq: LIV 2, IVE 2, VE  1, E A 1,  AN 1, AND 1, ND  1, D L 1,  LE 1, LET 1, ET  1, T L 1,  LI 1
  alphabetic:  AN 1,  LE 1,  LI 1, AND 1, D L 1, E A 1, ET  1, IVE 2, LET 1, LIV 2, ND  1, T L 1, VE  1
  alpha/freq: IVE 2, LIV 2,  AN 1,  LE 1,  LI 1, AND 1, D L 1, E A 1, ET  1, LET 1, ND  1, T L 1, VE  1
There are thirteen unique 4-grams:
    original: LIVE 2, IVE  1, VE A 1, E AN 1,  AND 1, AND  1, ND L 1, D LE 1,  LET 1, LET  1, ET L 1, T LI 1,  LIV 1
   orig/freq: LIVE 2, IVE  1, VE A 1, E AN 1,  AND 1, AND  1, ND L 1, D LE 1,  LET 1, LET  1, ET L 1, T LI 1,  LIV 1
  alphabetic:  AND 1,  LET 1,  LIV 1, AND  1, D LE 1, E AN 1, ET L 1, IVE  1, LET  1, LIVE 2, ND L 1, T LI 1, VE A 1
  alpha/freq: LIVE 2,  AND 1,  LET 1,  LIV 1, AND  1, D LE 1, E AN 1, ET L 1, IVE  1, LET  1, ND L 1, T LI 1, VE A 1

Python[edit]

This example generates n-grams lazily, much like the sliding_window recipe from the Python itertools docs. 

from collections import Counter
from collections import deque
from itertools import islice


def n_grams(text, n):
    """Generate contiguous sequences of _n_ characters from _text_."""
    it = iter(text.upper())
    ngram = deque(islice(it, n), maxlen=n)
    if len(ngram) == n:
        yield "".join(ngram)
    for ch in it:
        ngram.append(ch)
        yield "".join(ngram)


if __name__ == "__main__":
    import pprint

    example = "Live and let live"

    for n in range(2, 5):
        result = Counter(n_grams(example, n)).most_common()
        print(
            f"{len(result)} {n}-grams of {example!r}:\n",
            pprint.pformat(result, compact=True),
            end="\n\n",
        )
Output:
12 2-grams of 'Live and let live':
 [('LI', 2), ('IV', 2), ('VE', 2), (' L', 2), ('E ', 1), (' A', 1), ('AN', 1),
 ('ND', 1), ('D ', 1), ('LE', 1), ('ET', 1), ('T ', 1)]

13 3-grams of 'Live and let live':
 [('LIV', 2), ('IVE', 2), ('VE ', 1), ('E A', 1), (' AN', 1), ('AND', 1),
 ('ND ', 1), ('D L', 1), (' LE', 1), ('LET', 1), ('ET ', 1), ('T L', 1),
 (' LI', 1)]

13 4-grams of 'Live and let live':
 [('LIVE', 2), ('IVE ', 1), ('VE A', 1), ('E AN', 1), (' AND', 1), ('AND ', 1),
 ('ND L', 1), ('D LE', 1), (' LET', 1), ('LET ', 1), ('ET L', 1), ('T LI', 1),
 (' LIV', 1)]

Raku[edit]

sub n-gram ($this, $N=2) { Bag.new( flat $this.uc.map: { .comb.rotor($N => -($N-1))».join } ) }
dd 'Live and let live'.&n-gram; # bi-gram
dd 'Live and let live'.&n-gram(3); # tri-gram
Output:
("IV"=>2,"T "=>1,"VE"=>2,"E "=>1,"LE"=>1,"AN"=>1,"LI"=>2,"ND"=>1,"ET"=>1," L"=>2," A"=>1,"D "=>1).Bag
("ET "=>1,"AND"=>1,"LIV"=>2," LI"=>1,"ND "=>1," LE"=>1,"IVE"=>2,"E A"=>1,"VE "=>1,"T L"=>1,"D L"=>1,"LET"=>1," AN"=>1).Bag

RPL[edit]

Works with: Halcyon Calc version 4.2.8
RPL code Comment 
≪ → text n 
   ≪ { } DUP n text SIZE FOR j 
       text j n - 1 + j SUB 
       IF DUP2 POS THEN 
          LAST 4 ROLL SWAP DUP2 GET 1 + PUT 
          SWAP DROP SWAP 
       ELSE + SWAP 1 + SWAP END 
     NEXT SHOWG 
≫ ≫ ‘-GRAMS’ STO

≪ { } 1 3 PICK SIZE FOR j 
      OVER j GET "=" + 4 PICK j GET →STR + + NEXT 
   ROT ROT DROP2
 ≫ ‘SHOWG’ STO

-GRAMS ( text n -- { "ngram=count".. } ) 
Initialize 2 empty lists; for j = n to length(text):
  ngram = text[j-n+1..j]
  if ngram already in ngram list
    increase counter in other list
    get rid of ngram
  else add to ngram list and set counter at 1 on the other list
Show results


SHOWG ( { "ngram".. } { counts.. } -- { "ngram=count".. } )
Input:
"LIVE AND LET LIVE" 2 -GRAMS
"LIVE AND LET LIVE" 3 -GRAMS
"LIVE AND LET LIVE" 4 -GRAMS
Output:
3: { "LI=2" "IV=2" "VE=2" "E =1" " A=1" "AN=1" "ND=1" "D =1" " L=2" "LE=1" "ET=1" "T =1" }
2: { "LIV=2" "IVE=2" "VE =1" "E A=1" " AN=1" "AND=1" "ND =1" "D L=1" " LE=1" "LET=1" "ET =1" "T L=1" " LI=1" }
1: { "LIVE=2" "IVE =1" "VE A=1" "E AN=1" " AND=1" "AND =1" "ND L=1" "D LE=1" " LET=1" "LET =1" "ET L=1" "T LI=1" " LIV=1" }

Wren[edit]

Version 1 (Sorted order)[edit]

Library: Wren-str
Library: Wren-maputil
Library: Wren-fmt
import "./str" for Str
import "./maputil" for MultiSet
import "./fmt" for Fmt

var findNgrams = Fn.new { |n, text|
    text = Str.upper(text)
    var ngrams = {}
    for (i in 0..text.count-n) {
        var ngram = text[i...i+n]
        MultiSet.add(ngrams, ngram)
    }
    return ngrams
}

// sort by decreasing frequency, then by lexicographical order
var comparer = Fn.new { |i, j|
    if (i.value != j.value) return j.value < i.value
    return Str.lt(i.key, j.key)
}

var text = "Live and let live"
for (n in [2, 3, 4]) {
    var ngrams = findNgrams.call(n, text)
    System.print("All %(n)-grams of '%(text)' and their frequencies:")
    var ng = ngrams.toList.sort(comparer).map { |me| "(\"%(me.key)\" : %(me.value))"}
    Fmt.tprint("$s  ", ng, 5)
    System.print()
}
Output:
All 2-grams of 'Live and let live' and their frequencies:
(" L" : 2)   ("IV" : 2)   ("LI" : 2)   ("VE" : 2)   (" A" : 1)   
("AN" : 1)   ("D " : 1)   ("E " : 1)   ("ET" : 1)   ("LE" : 1)   
("ND" : 1)   ("T " : 1)   

All 3-grams of 'Live and let live' and their frequencies:
("IVE" : 2)   ("LIV" : 2)   (" AN" : 1)   (" LE" : 1)   (" LI" : 1)   
("AND" : 1)   ("D L" : 1)   ("E A" : 1)   ("ET " : 1)   ("LET" : 1)   
("ND " : 1)   ("T L" : 1)   ("VE " : 1)   

All 4-grams of 'Live and let live' and their frequencies:
("LIVE" : 2)   (" AND" : 1)   (" LET" : 1)   (" LIV" : 1)   ("AND " : 1)   
("D LE" : 1)   ("E AN" : 1)   ("ET L" : 1)   ("IVE " : 1)   ("LET " : 1)   
("ND L" : 1)   ("T LI" : 1)   ("VE A" : 1)

Version 2 (Original order)[edit]

Library: Wren-ordered

The iteration order of 'Map' objects in Wren is undefined though they can subsequently be sorted into a particular order as the first version shows. However, to maintain the original order of insertion we need to use one of the classes in the above module which automatically keep track of such order when items are added or removed. 

import "./str" for Str
import "./ordered" for OrderedBag
import "./fmt" for Fmt

var findNgrams = Fn.new { |n, text|
    text = Str.upper(text)
    var ngrams = OrderedBag.new()
    for (i in 0..text.count-n) {
        var ngram = text[i...i+n]
        ngrams.add(ngram)
    }
    return ngrams
}

var text = "Live and let live"
for (n in [2, 3, 4]) {
    var ngrams = findNgrams.call(n, text)
    System.print("All %(n)-grams of '%(text)' and their frequencies:")
    var ng = ngrams.toList.map { |me| "(\"%(me.key)\" : %(me.value))"}
    Fmt.tprint("$s  ", ng, 5)
    System.print()
}
Output:
All 2-grams of 'Live and let live' and their frequencies:
("LI" : 2)   ("IV" : 2)   ("VE" : 2)   ("E " : 1)   (" A" : 1)  
("AN" : 1)   ("ND" : 1)   ("D " : 1)   (" L" : 2)   ("LE" : 1)  
("ET" : 1)   ("T " : 1)  

All 3-grams of 'Live and let live' and their frequencies:
("LIV" : 2)   ("IVE" : 2)   ("VE " : 1)   ("E A" : 1)   (" AN" : 1)  
("AND" : 1)   ("ND " : 1)   ("D L" : 1)   (" LE" : 1)   ("LET" : 1)  
("ET " : 1)   ("T L" : 1)   (" LI" : 1)  

All 4-grams of 'Live and let live' and their frequencies:
("LIVE" : 2)   ("IVE " : 1)   ("VE A" : 1)   ("E AN" : 1)   (" AND" : 1)  
("AND " : 1)   ("ND L" : 1)   ("D LE" : 1)   (" LET" : 1)   ("LET " : 1)  
("ET L" : 1)   ("T LI" : 1)   (" LIV" : 1)

XPL0[edit]

int Dict(100), Count(100), Size;

proc LookUp(Wd);        \Add word to dictionary, or increment its count
int  Wd, I;
[for I:= 0 to Size-1 do
    if Dict(I) = Wd then
        [Count(I):= Count(I)+1;
        return;
        ];
Dict(Size):= Wd;
Count(Size):= 1;
Size:= Size+1;
];

proc ShowNGram(N, Str); \Show N-grams for string
char N, Str;
int  I, J, Wd, Ch;
[IntOut(0, N);  Text(0, "-grams:^m^j");
Size:= 0;  I:= 0;
loop    [Wd:= 0;
        for J:= 0 to N-1 do
            [Ch:= Str(I+J);
            if Ch = $A0 then quit;      \terminating space
            if Ch>=^a and Ch<=^z then Ch:= Ch & ~$20;
            Wd:= Wd<<8 + Ch;
            ];
        I:= I+1;
        LookUp(Wd);
        ];
for I:= 0 to Size-1 do
    [Wd:= Dict(I);
    for J:= N-1 downto 0 do
        ChOut(0, Wd>>(J*8));
    ChOut(0, ^ );
    IntOut(0, Count(I));
    if rem(I/5) = 4 then CrLf(0) else ChOut(0, 9\tab\);
    ];
CrLf(0);
];

int N;
for N:= 2 to 4 do ShowNGram(N, "Live and let live ")
Output:
2-grams:
LI 2    IV 2    VE 2    E  1     A 1
AN 1    ND 1    D  1     L 2    LE 1
ET 1    T  1    
3-grams:
LIV 2   IVE 2   VE  1   E A 1    AN 1
AND 1   ND  1   D L 1    LE 1   LET 1
ET  1   T L 1    LI 1   
4-grams:
LIVE 2  IVE  1  VE A 1  E AN 1   AND 1
AND  1  ND L 1  D LE 1   LET 1  LET  1
ET L 1  T LI 1   LIV 1
Retrieved from "https://rosettacode.org/w/index.php?title=N-grams&oldid=344509"