cedric's bazaar - cs_lang

ackermann

anonymous@undisclosed.example.com (Anonymous) — Fri, 10 Jul 2020 07:48:28 +0000

You can clone this repository to get the source code.

Different implementations

Objective Caml

let rec ackermann x y = match (x,y) with
    | (0, _) -> y + 1
    | (_ , 0) -> ackermann (x - 1) 1
    | (_, _) -> ackermann (x - 1) (ackermann x (y - 1));;

Haskell

ackermann :: Integer -> Integer -> Integer
ackermann 0 y = y + 1
ackermann x 0 = ackermann (x-1) 1
ackermann x y = ackermann (x-1) $ ackermann x (y-1)

Python

def ackermann(m, n):
    if m == 0:
        return n + 1
    elif n == 0:
        return ackermann(m - 1, 1)
    else:
        return ackermann(m - 1, ackermann(m, n - 1))

def ackermann(m, n):
    while m >= 4:
        if n == 0:
            n = 1
        else:
            n = ackermann(m, n - 1)
        m -= 1
    if m == 3:
        return (1 << n + 3) - 3
    elif m == 2:
        return (n << 1) + 3
    elif m == 1:
        return n + 2
    else:
        return n + 1

Some values of Ackermann

Ackermann 3 n

Ackermann 3 1

Ackermann 3 2

Ackermann 3 1000

85720688574901385675874003924800144844912384936442688595500031069628084089994889799455870305255668650207573833404251746014971622855385123487876620597588598431476542198593847883368596840498969135023633457224371799868655530139190140473324351568616503316569571821492337341283438653220995094697645344555005

Ackermann 4 n

Ackermann 4 1

Ackermann 4 2

20035299304068464649790723515602557504478254755697514192650169737108940595563114530895061308809333481010382343429072631818229493821188126688695063647615470291650418719163515879663472194429309279820843091048559905701593189596395248633723672030029169695921561087649488892540908059114570376752085002066715637023661263597471448071117748158809141357427209671901518362825606180914588526998261414250301233911082736038437678764490432059603791244909057075603140350761625624760318637931264847037437829549756137709816046144133086921181024859591523801953310302921628001605686701056516467505680387415294638422448452925373614425336143737290883037946012747249584148649159306472520151556939226281806916507963810641322753072671439981585088112926289011342377827055674210800700652839633221550778312142885516755540733451072131124273995629827197691500548839052238043570458481979563931578535100189920000241419637068135598404640394721940160695176901561197269823378900176415171900511334663068981402193834814354263873065395529696913880241581618595611006403621197961018595348027871672001226046424923851113934004643516238675670787452594646709038865477434832178970127644555294090920219595857516229733335761595523948852975799540284719435299135437637059869289137571537400019863943324648900525431066296691652434191746913896324765602894151997754777031380647813423095961909606545913008901888875880847336259560654448885014473357060588170901621084997145295683440619796905654698136311620535793697914032363284962330464210661362002201757878518574091620504897117818204001872829399434461862243280098373237649318147898481194527130074402207656809103762039992034920239066262644919091679854615157788390603977207592793788522412943010174580868622633692847258514030396155585643303854506886522131148136384083847782637904596071868767285097634712719888906804782432303947186505256609781507298611414303058169279249714091610594171853522758875044775922183011587807019755357222414000195481020056617735897814995323252085897534635470077866904064290167638081617405504051176700936732028045493390279924918673065399316407204922384748152806191669009338057321208163507076343516698696250209690231628593500718741905791612415368975148082619048479465717366010058924766554458408383347905441448176842553272073155863493476051374197795251903650321980201087647383686825310251833775339088614261848003740080822381040764688784716475529453269476617004244610633112380211345886945322001165640763270230742924260515828110703870183453245676356259514300320374327407808790562836634069650308442258559670392718694611585137933864756997485686700798239606043934788508616492603049450617434123658283521448067266768418070837548622114082365798029612000274413244384324023312574035450193524287764308802328508558860899627744581646808578751158070147437638679769550499916439982843572904153781434388473034842619033888414940313661398542576355771053355802066221855770600825512888933322264362819848386132395706761914096385338323743437588308592337222846442879962456054769324289984326526773783731732880632107532112386806046747084280511664887090847702912081611049125555983223662448685566514026846412096949825905655192161881043412268389962830716548685255369148502995396755039549383718534059000961874894739928804324963731657538036735867101757839948184717984982469480605320819960661834340124760966395197780214411997525467040806084993441782562850927265237098986515394621930046073645079262129759176982938923670151709920915315678144397912484757062378046000099182933213068805700465914583872080880168874458355579262584651247630871485663135289341661174906175266714926721761283308452739364692445828925713888778390563004824837998396920292222154861459023734782226825216399574408017271441461795592261750838890200741699262383002822862492841826712434057514241885699942723316069987129868827718206172144531425749440150661394631691976291815065797455262361912248480638900336690743659892263495641146655030629659601997206362026035219177767406687774635493753188995878662821254697971020657472327213729181446666594218720034745089428309115351892711142871083761592223802766053278233516615551493693757784666701457179719012271178127804502400263847587883393968179629506907988171216906869295382485298300234760684541141781391106485602365497542274972310076151318700240539105109138178437217914225285874320985249578780346837033378184214440171386881242499844186181292711985333153825673218704215306311977485352146709553346263366108646673322924098798492566911095161436186015489097402419135096230436121961281659505186660220307156136847323646608689050142639139065150639081993788523183650598972991254044794434251667742996598118492331515552728832740283526884424087528112832899806259126736995462473415433335001472314306127503903073971352520693381738433229507010490618675394331307847980156551303847581556852362180104196502555961819349863159132330360964619059902361126811960234418433633345949276319461017166529138237171823942992162725384617760656945422978770713831988170369645886898118632109769003557358846244648357062914530527571012788720279653644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awk

anonymous@undisclosed.example.com (Anonymous) — Mon, 30 Apr 2012 07:30:21 +0000

Simple examples

Compare two files

{
if (ancien == FILENAME)
	A[NR] = $0
else {
	if (ok == 1)  {
		NR = 1
		ok = 0 }
	B[NR] = $0 }
}
END {printf("%s", A[2])
	for(i=0 ; i <= NR ; i++) {
		for(j=1 ; j<length(A[i]) ; j++) {
			if (substr(A[i],j,1) != substr(B[i],j,1)) {
				printf("diff : %s\t%d\t%d",substr(A[i],j,1), i, j)
			}
		}
	}
}

Round time

ligne=""
{ for(i=1; i<=NF; i++) {
	if ($i !~ /^[0-2][0-9]:[0-5][0-9]:[0-5][0-9]$/)
		ligne=ligne" "$i
	else
	{
		split($i,T,":")
		T[3]=int((T[3]+5)/10)*10
		if (T[3]==60)
		{
			T[3]="00"
			T[2]++
			if (T[2]==60)
			{
				T[2]="00"
				T[1]++
			}
		}
		if (T[3] == 0) T[3] = "00"
		ligne=ligne" "T[1]":"T[2]":"T[3]
	}
}
print ligne
}

Replace (tr)

BEGIN {c1="i"; c2="I"}
{
for(i=1 ; i <= length($0) ; i++) {
	if (substr($0,i,1) == c1)
		printf("%c",c2)
	else
		printf("%c",substr($0,i,1)) }
printf("\n")
}

uniq

BEGIN { option = "" }
{ if ($0 == precedent)  i++
else { printf("\t%d\t%s\n", i, precedent)
	i=0 }
precedent = $0 }

c

anonymous@undisclosed.example.com (Anonymous) — Sun, 30 Sep 2012 21:32:26 +0000

Learning C

The C Programming Language.

Simple examples

Hello World

/* Hello World program */
 
#include<stdio.h>
 
main()
{
    printf("Hello World");
}

Compile and run the program:

$ gcc -Wall hello.c -o hello.out
hello.c:6: warning: return type defaults to ‘int’
hello.c: In function ‘main’:
hello.c:10: warning: control reaches end of non-void function
 
$ ./hello.out 
Hello World

Increment a number

#include "stdio.h"
 
char  line[100];
int   value;
 
int main()
{
    printf("Enter a value:");
    fgets(line, sizeof(line), stdin);
    sscanf(line, "%d", &value);
 
    printf("Inc: %d\n", value + 1);
 
    return 0;
}

$ gcc -Wall test1.c 
cedric@debian:~$ ./a.out 
Enter a value:41
Inc: 42

Equivalent in python

>>> def inc():
...     value = raw_input("Enter a value:")
...     print "Inc:", int(value)+1
... 
>>> inc()
Enter a value:41
Inc: 42

Read a file

#include <stdio.h>   /* required for file operations */
 
FILE *fr;            /* declare the file pointer */
 
main()
{
   char line[1024];
   fr = fopen ("./file.txt", "rt");  /* open the file for reading */
   /* "rt" means open the file for reading text */
 
   while(fgets(line, 1024, fr) != NULL)
   {
         printf ("%s\n", line);
   }
   fclose(fr);  /* close the file prior to exiting the routine */
}

Equivalent in python

for line in open("./file.txt", "r"):
    print line

go

anonymous@undisclosed.example.com (Anonymous) — Fri, 18 Apr 2014 21:19:01 +0000

Learning Go

A Tour of Go.

Simple examples

Sum the elements of a list

package main
 
import "fmt"
 
func sum(a []int, c chan int) {
    sum := 0
    for _, v := range a {
        sum += v
    }
    c <- sum  // send sum to c
}
 
func main() {
    a := []int{7, 2, 8, -9, 4, 0}
 
    c := make(chan int)
    go sum(a[:len(a)/2], c)
    go sum(a[len(a)/2:], c)
    x, y := <-c, <-c
 
    fmt.Println(x, y, x + y)
}

Producer-consumer problem

package main
 
import ("fmt")
 
var done = make(chan bool)
var cake = make(chan int)
 
func produce (firstname string) {
    for i := 0; i < 10; i++ {
        fmt.Printf("%s make cake %d\n", firstname, i)
        cake <- i
    }
    done <- true
}
 
func consume (firstname string) {
    for {
      cake_number := <-cake
      fmt.Printf("%s eat cake %d\n", firstname, cake_number)
   }
}
 
func main () {
   go produce("Alice")
   go consume("Bob")
   go consume("Maxime")
   <- done
}

Fork bomb

package main
 
import "fmt"
 
func main() {
    c := make(chan bool)
    go func() {
        count := 0
        for <- c {
            count++
            fmt.Println(count)
        }
    }()
    bomb(c)
}
 
func bomb(tick chan bool) {
    for {
        tick <- true
        go bomb(tick)
    }
}

Books

Various resources.

haskell

anonymous@undisclosed.example.com (Anonymous) — Mon, 30 Apr 2012 14:51:29 +0000

Presentation

Paradigm

purely-functional;
lazy evaluation.

Typing discipline

static typed;
strongly typed;
inferred.

Learning Haskell

The Haskell Programming Language

Simple examples

You can compare functions below with the Objective Caml version.

Increment a number

let inc = (+) n
 
-- Alternative:
let inc n = succ n

Caesar cipher

-- Shifts a character to the right if positive, left if negative.
shift :: Int -> Char -> Char
shift n c | isUpper c = chr $ ord 'A' + ((ord c + n - ord 'A') `mod` 26)
          | isLower c = chr $ ord 'a' + ((ord c + n - ord 'a') `mod` 26)
          | otherwise = c
 
 
encode :: Int -> String -> String
encode _  [] = []
encode n  xs = map (shift n) xs

Parity

parity :: Integral a => [a] -> [Bool]
-- Using recursion
parity [] = []
parity (x:list) = [even x] ++ parity list
 
-- Using map
parity list = map even list

ocaml

anonymous@undisclosed.example.com (Anonymous) — Sun, 29 Apr 2012 09:44:30 +0000

Presentation

Paradigm

multi-paradigm: imperative, functional, object-oriented.

Typing discipline

static typed;
strongly typed;
inferred.

Learning Objective Caml

Simple examples

Increment a number

# let inc n = n+1;;
val inc : int -> int = <fun>
 
# inc 2;;
- : int = 3
 
 
# Alternative:
# let inc = (+) 1;;
val inc : int -> int = <fun>

Equivalent in Python

>>> def inc(n):
...     return n+1
 
>>> inc(2)
3

Great common divisor

# let rec gcd a b = match (a mod b) with
  | 0 -> b
  | c -> gcd b c;;
val gcd : int -> int -> int = <fun>
 
# gcd 77 42;;
- : int = 7

Equivalent in Python

def gcd(a, b):
    while b != 0:
        (a, b) = (b, a%b)
    return a

Parity

let rec parity = function
  | [] -> []
  | x::l -> (x mod 2 == 0)::(parity l);;
val func : int list -> bool list = <fun>
 
parity [1;2;3;4;5;6;7;8;9];;
- : bool list = [false; true; false; true; false; true; false; true; false]

Equivalent in Python

>>> l = [1,2,3,4,5,6,7,8,9]
>>> [(a % 2 == 0) for a in l]
[False, True, False, True, False, True, False, True, False]

Ackermann

let rec ackermann x y = match (x,y) with
    | (0, _) -> y + 1
    | (_ , 0) -> ackermann (x - 1) 1
    | (_, _) -> ackermann (x - 1) (ackermann x (y - 1));;

Equivalent in Python

def ackermann(m, n):
    if m == 0:
        return n + 1
    elif n == 0:
        return ackermann(m - 1, 1)
    else:
        return ackermann(m - 1, ackermann(m, n - 1))

Factorielle

let rec factorielle = function
  0 -> 1
| n -> n * factorielle (n - 1) ;;

(* Longueur d'une liste *)
# let rec longueur = function
      [] -> 0
    | t :: q -> 1 + longueur q ;;

let rec exists p = function
      [] -> false
    | a::l -> p==a || exists p l;;

python

anonymous@undisclosed.example.com (Anonymous) — Fri, 08 Aug 2025 22:44:00 +0000

Presentation

Paradigm

multi-paradigm: object-oriented, imperative, functional, procedural, reflective;
eager evaluation.

Typing discipline

duck;
dynamically typed;
strongly typed.

Learning Python

Python Programming Language – Official Website;
Style Guide for Python Code (PEP 0008) (to read before programming with Python);
The Python Challenge (learning is fun);
Popular Python recipes.

Books

Dive Into Python, by Mark Pilgrim;
Expert Python Programming, by Tarek Ziadé;
Programming in Python 3, by Mark Summerfield;
Dive Into Python 3, by Mark Pilgrim.

Various resources.

books, DiveIntoPython, python, AFPY