Programmeerimiskeeled. Sissejuhatus informaatikasse Aivar Annamaa 28. november 2012

Transcription

1 Programmeerimiskeeled Sissejuhatus informaatikasse Aivar Annamaa 28. november 2012

2 Mis on programmeerimiskeeled? Miks on prog.keeli nii palju? Kuidas prog.keeli tehakse?

3 Milleks programmeerimiskeeled?

4 Ülesanne => masin

5

6 Andmed Masin Väljund

7 Andmed Masin Programm Väljund

8 ENIAC 1946

9

10 Ülesanne => programm => masin

11 .equ lower,12.equ upper, 16 #;; [ebp+8] is start address, [ebp+12] is end address of partition _quicksort: push %ebp mov %ebp,%esp #pushad movl %ebx,12(%ebp) #; start of partition #;; find pivot index: ploop: cmp %ebx,16(%ebp) #; last cell of partition? jge qretrn #; no pivot, so exit movl %eax, 4(%ebx) #; A[i+1] cmp %eax, (%ebx) #; A[i] jl pfound #; A[i]>A[i+1], pivot found addl %ebx,4 #; next cell jmp ploop pfound: #;; at this point, ebx holds mem address of pivot #;; now partition into < and >= pivot via repeated swapping. #;; use two counters: ebx and esi. ebx always points to the #;; first cell of second partition (what's >= pivot) movl %ecx,(%ebx) #; save pivot in ecx movl %esi,%ebx addl %esi,4 #; next cell tloop: #; partitioning loop cmp %ecx,(%esi) #; compare pivot against element jle noswap #; no swap if element >=pivot #;; swap [ebx] and [esi], advance both movl %eax,(%ebx) pushl %eax #; use stack as temp movl %eax,(%esi) movl (%ebx),%eax popl %eax movl (%esi),%eax #; done swap addl %ebx,4 #; next cell must still be >= pivot noswap: addl %esi,4 #; goto next cell, preserve ebx cmp %esi,16(%ebp) #; end of partition? jle tloop #; next iteration of partition loop #;; #;; #;; at this point, ebx holds start addr of second partition (could be pivot itself). make recursive calls to quickaux: #;; first partition: subl %ebx,4 pushl %ebx #; movl %eax,12(%ebp) pushl %eax #; call _quicksort addl %esp,8 #; #;; second partition movl %eax,16(%ebp) pushl %eax #; addl %ebx,4 push %ebx #; call _quicksort addl %esp,8 qretrn: end of first paritition start of first partition deallocate params end of second partition start of second partition Assembler-keeled cmp %ecx,(%esi) jle noswap movl %eax,(%ebx) pushl %eax movl %eax,(%esi) movl (%ebx),%eax popl %eax movl (%esi),%eax addl %ebx,4

12 Ülesanne => programm => masin

13

14 Fortran (1957) i = 1 sum = 0 10 do 20 i = 1, 50 if (i.gt. 10) goto 30 sum = sum + i 20 continue 30 if (i. le. 20) then sum = sum 1 goto 20 else sum = 2*sum endif write(*,*) 'Sum =', sum

15 Transleerimine

16 Kui palju on prog.keeli?

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18

19 The Zen of Python >>> import this The Zen of Python, by Tim Peters Beautiful is better than ugly. Explicit is better than implicit. Simple is better than complex. Complex is better than complicated. Flat is better than nested. Sparse is better than dense. Readability counts. Special cases aren't special enough to break the rules. Although practicality beats purity. Errors should never pass silently. Unless explicitly silenced. In the face of ambiguity, refuse the temptation to guess. There should be one-- and preferably only one --obvious way to do it. Although that way may not be obvious at first unless you're Dutch. Now is better than never. Although never is often better than *right* now. If the implementation is hard to explain, it's a bad idea. If the implementation is easy to explain, it may be a good idea. Namespaces are one honking great idea -- let's do more of those!

20 Perl: TIMTOWTDI "There Is More Than One Way To Do It"

21 Paindlik vs. täpne/range

22 def arvuta(a, b): if a == 23: return 3 else: return a / b print(arvuta(23, "tere"))

23 public class RangeLugu { public static void main(string[] args) { System.out.println(divide(23, "tere")); } private static int arvuta(int a, int b) { if (a == 23) { return 3; } else { return a / b; } } }

24 requires 0 < amount && amount <= balance; //@ assignable balance; //@ ensures balance == \old(balance) - amount; public void debit(final int amount) { this.balance -= amount; } //@ requires!islocked; //@ ensures \result == balance; //@ also //@ requires islocked; //@ signals_only BankingException; public /*@ int getbalance() throws BankingEx { if (!this.islocked) { return this.balance; } else { throw new BankingException(); } }

25 Universaalne vs spetsiifiline

26 Prolog (1972) mother_child(trude, sally). father_child(tom, sally). father_child(tom, erica). father_child(mike, tom). sibling(x, Y) :- parent_child(z, X), parent_child(z, Y). parent_child(x, Y) :- father_child(x, Y). parent_child(x, Y) :- mother_child(x, Y).?- sibling(sally, erica). Yes

27 LISP (1958) Scheme Common Lisp Clojure (def x (+ 3 (* 4 2) 6)) John McCarthy

28 Domeenispetsiifilised keeled (DSL-s)

29 HTML <span style="font-size:10px; color: gray"> AEGEE-Tallinn<br/> <a href=" style="color:gray"> </span> </td> <!-- Contents > <td class="right"> <p> <a class='pic right' href='pics/tree_big.jpg'><img src='pics/tree_sm.jpg' alt='tree' /></a> </p> <div style="font-size:10px">aegee-tallinn proudly presents:</div> <div style="font-size:28px; font-weight:bold; margin-top:25px; margin-bottom:5px">

30 CSS body.toc span.remark { color: gray; font-style: normal; font-weight: 900; } /* LAYOUT *** */ body { text-align:center; } html, body { height: 100%; padding: 0px; margin: 0px; }

31 SQL (1974) SELECT FROM ON GROUP Book.title, COUNT(*) AS Authors Book JOIN Book_author Book.isbn = Book_author.isbn BY Book.title; Title SQL Examples and Guide The Joy of SQL An Introduction to SQL Pitfalls of SQL Authors

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33 Keelte rühmitamine Imperatiivne vs. deklaratiivne Dünaamiline vs. staatiline Üldotstarbeline vs. domeenispetsiifiline

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35

36 Universaalne programmeerimiskeel?

37 Newspeak (George Orwell, "1984")

38 Programmeerime mõnes loomulikus (nt. inglise) keeles?

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40 Clojure Haskell Io Prolog Scala Erlang Ruby

41 Millest programmeerimiskeeled tehtud on?

42 KJK - Kilpkonna Juhtimise Keel E V E V E

43 Kilpkonna juhtija import turtle f = open("kilpkonn.txt", encoding="utf-8") for käsk in f: osad = käsk.split() tüüp = osad[0] argument = int(osad[1]) if tüüp == 'E': turtle.forward(argument) elif tüüp == 'T': turtle.backward(argument) elif tüüp == 'V': turtle.left(argument) elif tüüp == 'P': turtle.right(argument) else: print("tundmatu käsk:", käsk) f.close() turtle.exitonclick()

44 Mis on loomulik keel? Tähestik Morfoloogia (sõnade moodustamise reeglid) Süntaks (lausete moodustamise reeglid) Avatud sõnavara (sõnad koos tähendusega) Mis on keele eesmärk?

45 Formaalne keel Mingi alfabeedi põhjal koostatud sõnade (programmide) hulk {a, aa, aaa, aaaa,...} {ab, ba, aa, bb} {0, 1, 10, 11, 101, 110, 111,...} {..., print ( "tere" ),...} Tavaliselt on igale sõnale (programmile) määratud ka mingi tähendus e. semantika Kuidas keelt defineerida? Kas loetleme kõik programmid ja nende tähendused?

46 Morfoloogia ja süntaks Reeglid, mis määravad kuidas on lubatud teha tähtedest sõnu sõnadest lauseid Võimaldavad kirjeldada lõpmatut hulka variatsioone Loomuliku keele morfoloogia ja süntaks kirjeldatakse tavaliselt loomulikus keeles Formaalse keele korral...

47 Pythoni süntaksi fragment if_stmt: 'if' test ':' suite ['else' ':' suite] test : or_test ['if' or_test 'else' test] or_test: and_test ('or' and_test)* suite :... if_stmt term : factor (('*' '/' '%' '//') factor)* factor : ('+' '-' '~') factor power... NAME : ('A'..'Z' 'a'.. 'z' '_')*

48 Konkreetne vs. abstraktne süntaks x = 3 * (y - z) (= x (* 3 (- y z)))

49 Süntaksi analüüs (ing.k parsing)

50 Tähendus e. semantika Interpretaatori kaudu (operatsiooniline semantika) Translaatori kaudu (denotatsiooniline semantika)

51 Interpreteerimine Kilpkonna interpretaator Python CPU Küllaltki lihtne realiseerida Samu asju tuleb mitu korda interpreteerida

52 Transleerimine (e. kompileerimine) javac gcc masm Keerulisem realiseerida Võtab aega Lähtekeele tõlgendamist pole vaja teha igal käivitusel

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54 KJK translaator Sisend: fail KJK käskudega Väljund: Pythoni fail

55 Palju tasemeid KJK Python C Assembler Masinkood JIT

56 Õiged primitiivid + kombineerimisreeglid => misiganes! Virtuaalne masin NAND + False Protsessor Assembler Prog. keel OP-süsteem Tetris html

57 ... kõik see jookseb op-süsteemis prog keelel... CPU-s... Veel üks näide:

58 Formaalne keel vs loomulik keel Mis on formaalse keele eesmärk? Kas formaalsetel keeltel on mõtet ilma arvutita?

59 Formaalne keel vs. loomulik keel Formaalne keel ei luba jätta asju hägusaks Probleem?

60 Programmide staatiline analüüs lvor/

61 Programmeerimiskeeled ja ATI Uurimissuunad Funktsionaalsed keeled Kategooriate teooria Programmide staatiline analüüs Tüübiteooria

62 Python (1991) def ühend(j1, j2): tulemus = [] for element in j1: if not (element in tulemus): tulemus.append(element) for element in j2: if not (element in tulemus): tulemus.append(element) return tulemus print(ühend([1, 2, 3, 2], [1, 6, 6])) Guido van Rossum (BDFL)

63 Java (1995) JVM Applets Web Java SE Java EE, Spring Android Seadmed James Gosling

64

65 JavaScript (1995) JS on igas arvutis! WEB 2.0 mootor... <script> function fact(n) { if (n == 0) { return 1; } return n * fact(n 1); } </script>...

66 PHP (1995) <html> <body> <ul> Rasmus Lerdorf <?php $ylesanded = file("todo.txt"); if (isset($_post['ylesanne'])) { $ylesanded[] = $_POST['ylesanne']; file_put_contents("todo.txt", join("\n", $ylesanded)); }...

67 Ruby (1995) class Person attr_reader :name, :age def = name, age end def <=> person.age end def to_s "#@name (#@age)" end end group = [ Person.new("Bob", 33), Person.new("Chris", 16), Person.new("Ash", 23) ] まつもとゆきひろ (Matz)

68 Perl (1987) "There's more than one way to do it" if (m/\w/) { = split (//); my $A = my $Z = print $A; if (defined ($Z)) { my $i = $#w+1; while ($i--) { my $j = int rand Larry Wall

69 C #include <stdio.h> int main(void) { printf("hello,world\n"); return 0; }... int ar[5], *ip; ip = &ar[3];

70 C++ (1983) Bjarne Stroustrup... template <class mytype> mytype GetMax (mytype a, mytype b) { return (a>b?a:b); }...

71 Objective-C (1983) #import <stdio.h> #import "Fraction.h" int main( int argc, const char *argv[] ) { Fraction *frac = [[Fraction alloc] init]; [frac setnumerator: 1]; [frac setdenominator: 3]; printf( "The fraction is: " ); [frac print]; printf( "\n" ); [frac release]; return 0; }

72 C# using System; public class HelloWorld { public static void Main(string[] args) { Console.Write("Hello World!"); } }

73 Pascal (1970)

74 Haskell (1990) quicksort :: Ord a => [a] -> [a] quicksort [] = [] quicksort (p:xs) = (quicksort lesser) ++ [p] ++ (quicksort greater) where lesser = filter (< p) xs greater = filter (>= p) xs

75 Whitespace (2003)