Melakukan Operasi Logika

Transkripsi

1 Melakukan Operasi Logika

2 Hampir semua statemen C++ adalah ekspresi. Operator C++ selain +, -, /, * yakni operator logika. Pada dasarnya orang2 menghitung menggunakan operasi AND dan OR

3 Mengapa Menggunakan Operasi Logika Program C++ harus membuat Keputusan Membuat keputusan benar atau salah, butuh operasi logika

4 Tabel

5 Contoh n == 0; Apa bedanya dengan n = 0? Contoh Operator lebih besar (>) atau lebih kecil (<) : int n1 = 1; int n2 = 2; n1 < n2;

6 Contoh kombinasi operator && (AND), II (OR) dengan operator logika yang lain : // true if n2 is greater than n1 but n2 smaller than n3 // (this is the most common way determining that n2 is in // the range of n1 to n3, exclusive) (n1 < n2) && (n2 < n3);

7 Menyimpan Nilai Logika Hasil dari operasi logika dapat disimpan ke variabel yang bertipe bool : int n1 = 1; int n2 = 2; bool b; b = (n1 == n2); Apa bedanya antara operasi (=) dengan (==)

8 Program Mendemonstrasikan Variable bool // BoolTest - compare variables input from the // keyboard and store the results off // into a logical variable #include <cstdio> #include <cstdlib> #include <iostream> using namespace std; int main(int nnumberofargs, char* pszargs[]) { // set output format for bool variables // to true and false instead // of 1 and 0 cout.setf(cout.boolalpha);

9 // initialize two arguments int narg1; cout << Input value 1: ; cin >> narg1; int narg2; cout << Input value 2: ; cin >> narg2; bool b; b = narg1 == narg2;

10 cout << The statement, << narg1 << equals << narg2 << is << b << endl; // wait until user is ready before terminating program // to allow the user to see the program results } system( PAUSE ); return 0;

11 Tampilan program setelah di eksekusi : Input value 1: 5 Input value 2: 5 The statement, 5 equals 5 is true Press any key to continue...

12 Warning : Penggunaan Operasi Logika Pada Floating Point float f1 = 10.0; float f2 = f1 / 3; f1 == (f2 * 3.0); // are these two equal? Perbandingan ini tidak terlalu dibutuhkan.

13 Perhatikan problem berikut : float f1 = 10.0; float f2 = 100 % 30; f1 == f2; // are these two equal?

14 Perhatikan Command Berikut : float f1 = 10.0; float f2 = f1 / 3; float f3 = f2 * 3.0; (f1 - f3) < && (f3 - f1) < ;

15 Sistem Bilangan Sistem Bilangan Desimal : 123 = 1 * * * 1 atau 123 = 1 * * * 100 Sistem Bilangan Octal : = 1 * * * 80 = 1738 Sistem Bilangan Biner : = 0* *64 + 1*32 + 1*16 + 1*8 + 0*4 +1*2 + 1*1 =

16 Sistem Bilangan Hexadecimal : 123 = 7 * B (i.e. 11) * 160 = 7B16

17 Melakukan Operasi bitwise C++ Semua bilangan C++ diekspresikan ke dalam bentuk bilangan biner :

18 Operator Operator NOT : NOT 1 (true) is 0 (false) NOT 0 (false) is 1 (true) Operator AND : 1 (true) AND 1 (true) is 1 (true) 1 (true) AND 0 (false) is 0 (false) Operator OR : 1 (true) OR 0 (false) is 1 (true) 0 (false) OR 0 (false) is 0 (false)

19 Bitwise Operator

20 Penggunaan Operator Bitwise Operator NOT : ~01102 (0x6) (0x9) Dapat kita simpulkan ~(0x6) = (0x9) Operator & : &

21 0x & & 0x x Dapat kita simpulkan : 0x6 & 0x3 = 0x2 Tes : Berapakah nilai 0x6 & 0x3?

22 Simple Test Program berikut mengilustrasikan penggunaan operator bitwise : // BitTest - initialize two variables and output the // results of applying the ~,&, and ^ // operations #include <cstdio> #include <cstdlib> #include <iostream> using namespace std; int main(int nnumberofargs, char* pszargs[]) { // set output format to hexadecimal cout.setf(cout.hex);

23 // initialize two arguments int narg1; narg1 = 0x1234; int narg2; narg2 = 0x00ff; // now perform each operation in turn // first the unary NOT operator cout << Arg1 = 0x << narg1 << \n ; cout << Arg2 = 0x << narg2 << \n ; cout << ~narg1 = 0x << ~narg1 << \n ; cout << ~narg2 = 0x << ~narg2 << \n ;

24 // now the binary operators cout << narg1 & narg2 = 0x << (narg1 & narg2) << \n ; cout << narg1 narg2 = 0x << (narg1 narg2) << \n ; cout << narg1 ^ narg2 = 0x << (narg1 ^ narg2) << \n ; } // wait until user is ready before terminating program // to allow the user to see the program results system( PAUSE ); return 0;

25 Ekspresi pertama dari program kita, cout.setf(ios::hex), Mengeset format output dari default desimal ke hexadesimal.

26 Proses Program : Arg1 = 0x1234 Arg2 = 0xff ~narg1 = 0xffffedcb ~narg2 = 0xffffff00 narg1 & narg2 = 0x34 narg1 narg2 = 0x12ff narg1 ^ narg2 = 0x12cb Press any key to continue...

27 Mengontrol Aliran Program

28 Mengontrol Aliran Program Bentuk sederhana dari kontrol aliran adalah branch statement (statemen cabang) Dalam C++, branch statement diimplementasikan statement if : if (m > n) { // Path 1 //...instructions to be executed if // m is greater than n } else { // Path 2 //...instructions to be executed if not }

29 Program mendemonstrasikan statement if : // BranchDemo - input two numbers. Go down one path of the // program if the first argument is greater than // the first or the other path if not #include <cstdio> #include <cstdlib> #include <iostream> using namespace std; int main(int nnumberofargs, char* pszargs[]) { // input the first argument... int arg1; cout << Enter arg1: ; cin >> arg1;

30 //...and the second int arg2; cout << Enter arg2: ; cin >> arg2; // now decide what to do: if (arg1 > arg2) { cout << Argument 1 is greater than argument 2 << endl; } else { cout << Argument 1 is not greater than argument 2 << endl; }

31 } // wait until user is ready before terminating program // to allow the user to see the program results system( PAUSE ); return 0; Program ini membaca dua bilangan integer dari keyboard dan membandingkannya.

32 Hasil Eksekusi : Enter arg1: 5 Enter arg2: 6 Argument 1 is not greater than argument 2 Press any key to continue...

33 Looping Saat Kondisi bernilai TRUE Bentuk paling sederhana dari statement looping adalah loop while while(condition) { } //... repeatedly executed as long as condition is true

34 Contoh Program : // WhileDemo - input a loop count. Loop while // outputting astring arg number of times. #include <cstdio> #include <cstdlib> #include <iostream> using namespace std; int main(int nnumberofargs, char* pszargs[]) { // input the loop count int loopcount; cout << Enter loopcount: ; cin >> loopcount;

35 // now loop that many times while (loopcount > 0) { loopcount = loopcount - 1; cout << Only << loopcount << loops to go\n ; } } // wait until user is ready before terminating program // to allow the user to see the program results system( PAUSE ); return 0;

36 Hasil eksekusi : Enter loopcount: 5 Only 4 loops to go Only 3 loops to go Only 2 loops to go Only 1 loops to go Only 0 loops to go Press any key to continue...

37 Jika User memasukkan nilai negatif, maka program tidak melewati loop. Versi lain dari While yang jarang di gunakan yakni do... While do { //...the inside of the loop } while (condition); Apa perbedaannya dengan while?

38 Penggunaan Fitur autoincrement / autodecrement // now loop that many times while (loopcount > 0) { loopcount = loopcount - 1; cout << Only << loopcount << loops to go\n ; } Versi lain: while (loopcount > 0) { loopcount--; cout << Only << loopcount << loops to go\n ; }

39 Dengan Autodecrement : while (loopcount-- > 0) { cout << Only << loopcount << loops to go\n ; } Versi program yang menggunakan Autodecrement akan tereksekusi lebih cepat