ProgramareProcedurala2013-M7

7/25/2019 ProgramareProcedurala2013-M7

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Versiunea 2013 G. Albeanu, Programare Procedura, M7 1

Programare procedurala M7

Tehnici de programare C (P2)

Grigore ALBEANU

http://www.researcherid.com/rid/H-4522-2011


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Agenda

Pointeri. Elemente de baza(Recapitulare)

Pointeri la functii. Aplicatii

Macrodefinitii (Recapitulare)

Programare generica


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Pointeri - > elemente de baza

#include

int EqualStruct (void *, void *, long); int EqualStruct (void *rec1, void *rec2, long lung){

unsigned char *ptr1; unsigned char *ptr2; register long ctr;

for (

ptr1 = (unsigned char *)rec1, ptr2 = (unsigned char *)rec2, ctr = lung / sizeof(unsignedchar);

ctr; --ctr)

if (*ptr1++ != *ptr2++) return 0;

return1;

}

typedef struct { char a; int b;} MyStruct;

int main(void){

MyStruct s1, s2; *(int*)(&s1) = 0x55555561; s1.b = 42;

*(int*)(&s2) = 0x55555561; s2.b = 42;

printf("%d", EqualStruct((MyStruct *)(&s1), (MyStruct *)(&s2), sizeof(MyStruct)));

}

Modificati continutul

locatiilor. Afisati

adresele. Schimbati

ordinea variabilelor


4/20


Pointeri la functii

Functii ca argumenteale altor functii

Functii callback (inprogramarea orientatape evenimente /comenzi)

Prea multe stele(stars)?

int *(*f)(int *); /*

comentariu */ int *g(int *x){static int

a=1; a+=*x; return &a;}

f=g

#include

int *g(int *x){static int a=1; a+=*x;printf("%d\n", a); return &a;}

int main(void){

int zz = 5, i, n=5;

int *(*f)(int *)=NULL;f=g;

int *aa;

printf("%x\n", aa=f(&zz));

for (i=1; i


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Functii ca argumente ale altor functii(call back)

#include int int_sort( const void *a, const void *b ){

int xa = *(int*)a; int xb = *(int*)b;

if (xa < xb) return -1; else if (xa == xb) return 0; else return 1;

}

int main(void){int X[10]; int i;

for ( i = 0; i < 10; ++i ) X[ i ] = 10 - i;

qsort(X, 10 , sizeof(int), int_sort);

for (i = 0; i < 10; ++i) printf ( "%d\n" ,X[ i ] );return 0;

}Functiile se transmit prin pointeri, nu prin

valoare

http://www.cprogramming.com/tutorial/function-pointers.html

Lui qsort nu-I pasa de codul

functiei (aici int_sort).

Se spune ca este un apel call

back.


6/20


Functii ca argumente ale altor functii(moduri de abordare)

float ADD(float a, float b) { return a+b; }float SUB(float a, float b) { return a-b; }

float MUL(float a, float b) { return a*b; }

float DIV (float a, float b) { return a/b; }void OP(float a, float b, float (*ptF)(float,

float)){float rez = ptF(a, b); printf(%f, rez);}

Utilizare: OP(3.14, 2.71, &ADD); OP(3.14,2.71, SUB); /* cu &, fara & : comentariu*/


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Alte aspecte Compararea pointerilor

la functiiif(ptF>0){

if(ptF == &DIV)printf(Apel adresat lui DIV\n"); }

else

printf("Pointer ne initializat!!\n");

Intoarcerea unui pointer lao functie

Metoda 1: Direct

float (*GetOP(const char opCode))

(float, float){

switch(opCode){

case +: return &ADD;

case -: return &SUB;case *: return &MUL;

case /: return %DIV;

default: return NULL;

}

Metoda 2: Utilizare typedef

typedef float(*ptF)(float, float);

ptF GetOP(const char opCode){

switch(opCode){

case +: return &ADD;

case -: return &SUB;

case *: return &MUL;

case /: return %DIV;

default: return NULL;

}

Decodificati: http://unixwiz.net/techtips/reading-cdecl.html


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Dispatch tables acces la

componentele unui tablou director

struct entry{ char *command; int (*func)(int, int);};

struct entry table[] = { {"add", &add}, {"subtract", &subtract} };

int (*getDispatchPtr(char *comm))(int, int) {

int i;

for(i = 0; i < 2; i++) {

if (strcmp(table[i].command, comm) == 0) return table[i].func;}return 0;

}

/* Utilizare:*/

ptF pt = NULL;

.pt = getDispatchPtr("subtract");

.

int rez = (*pt)(100, 20);

http://www.cise.ufl.edu/class/cop4600su10/discussion/disc4/2.html

In computer science, a dispatch table is a table of pointers to

functions or methods. Use of such a table is

a common technique when implementing late binding

in object-oriented programming.


10/20


Bibliografie suplimentara (1)

http://www.codeguru.com/cpp/cpp/cpp_mfc/callbacks/article.php/c10557/Callback-Functions-Tutorial.htm

http://stackoverflow.com/questions/142789/what-is-a-callback-in-c-and-how-are-they-

implemented/147241#147241 http://ocw.mit.edu/courses/electrical-engineering-

and-computer-science/6-087-practical-programming-in-c-january-iap-2010/lecture-

notes/MIT6_087IAP10_lec08.pdf http://www.compileonline.com/compile_c_online.php


11/20


Macrodefinitii operatorul #

#define

#define nume subst

#define BUFFER_SIZE 1024

#define nume(parametri) subst

#define min(X, Y) ((X) < (Y) ? (X) : (Y))

Parametrii nu sunt substituiti in siruri de caractere cu exceptia situatieiin care este prezent # (op = stringification)

Fie codul

#define Avertizare_daca(EXP) \

do { if (EXP) fprintf (stderr, Atentie: " #EXP "\n"); } while (0)

Utilizare:

Avertizare_daca(x == 0);/* adica: do { if (x == 0) fprintf (stderr, Atentie: " "x == 0" "\n"); } while (0); */


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Macrodefinitii operatorul ##

#include


do { if (EXP) fprintf (stderr, "Atentie: " #EXP "\n"); } while (0)

#define COMMAND(NAME) { #NAME, NAME ## _command }

void quit_command(void){};

void help_command(void){};

struct command{

char *name;

void (*function) (void);

};

struct command commands[] ={

COMMAND (quit),

COMMAND (help),

};

int main(void){int x=0;

Avertizare_daca(x==0);

/* puts(commands[0].name); puts(commands[1].name); */

return 0;

}

#include


do { if (EXP) fprintf (stdout, "Atentie: " #EXP

"\n"); } while (0)

#define COMMAND(NAME) { #NAME, NAME ##

_command }

struct command{

char *name;

void (*function) (void);

};void quit_command(void){};

void help_command(void){};

int main(void){

int x=0;

struct command commands[] ={

COMMAND (quit),

COMMAND (help),};

puts(commands[1].name);

Avertizare_daca(x==0);

puts(commands[0].name);

return 0;

}Stderr, stdout ! Atentie !


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Programare generica

Utilizarea pointerilor (void *) Utilizarea macrodefinitiilor

Proiectul SGLIB (Templates in C++: STL)

(Generics/Colections in Java/C++)


14/20


Utilizarea pointerilor void *#include

#include

int main(){

int a[]={3,6,4,1,8},t=4,k;(k=cauta(a, sizeof(a)/sizeof(int), sizeof(int),&t)) ==-1?

printf("\nElement inexistent!!!") :

printf("\nElementul pe pozitia %d",k);

double b[]={3.5,6.2,4.9,28.15},el_r=6.2;

(k=cauta(b, sizeof(b)/sizeof(double), sizeof(double),

&el_r)) ==-1?printf("\nElement inexistent!!!") :

printf("\nElementul pe pozitia %d",k);

char *sir="Sir de caractere!!!", el_c='i';

(k=cauta(sir, strlen(sir), sizeof(char), &el_c)) ==-1?

printf("\nElement inexistent!!!") :printf("\nElementul pe pozitia %d",k);

}

#include

int cauta(void *v, int n, int dim_el,void *el){

char *ec=(char*)v;

for(int i=0; i


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Utilizarea Macrodefinitiilor (1)

/* Definitie Generica operator de concatenare */

#define GENERIC_MAX( TYPE ) \TYPE TYPE##_MAX( TYPE a, TYPE b ) \

{ \

return (a > b) ? a : b; \

}

pentru a genera:

int int_MAX( int a, int b )

{

return (a > b) ? a : b;

}

float float_MAX( float a, float b )

{

return (a > b) ? a : b;}

double double_MAX( double a, double b )

{

return (a > b) ? a : b;

}

GENERIC_MAX(int)

GENERIC_MAXfloat)GENERIC_MAX(double)

#include

/* Definitie generica operator de

concatenare */

#define GENERIC_MAX( TYPE ) \

TYPE TYPE##_MAX( TYPE a, TYPE b ) \

{ \

return (a > b) ? a : b; \

}

GENERIC_MAX( int )

GENERIC_MAX( float )GENERIC_MAX( double )

int main(void){

int x=10, y=20;

float a=2.3f, b=6.7f;

double u=3.14, v=6.28;

printf("%d\n", int_MAX(x, y));printf("%f\n", float_MAX(a, b));

printf("%f\n", double_MAX(u,v));

return 0;

}


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Demonstratie

http://www.compileonline.com/compile_c_online.php


17/20


Utilizarea Macrodefinitiilor (2)/*

DECL_NOD

Scop: Declarare nod de tip specificat.

*/#define DECL_NOD( TIP ) \

typedef struct _NOD_##TIP \

{ \

TYPE data; \

struct _NOD_##TIP *next; \

} NOD_##TIP;

/*

DEF_FUN( TIP )

Scop: Definirea unei functii pentru crearea unui nod de tip specificat.

*/

#define DEF_FUN( TIP ) \

NOD_##TYPE *NOD_NOU_##TIP( TIP data ) \

{ \

NOD_##TIP *NODnou = \

(NOD_##TYP *)malloc( sizeof( NOD_##TIP ) ); \NODnou->data = data; \

NODnou->next = NULL; \

return NODnou; \

}

http://cecilsunkure.blogspot.ro/2012/08/generic-programming-in-c.html


18/20


Tema -

Implementarea listelor inlantuite inLinux Kernel

http://www.cs.fsu.edu/~baker/devices/lxr/

http/source/linux/include/linux/list.h

http://isis.poly.edu/kulesh/stuff/src/klist/


19/20


Proiectul SGLIB

SGLIB API(?) generic pentru C -> ofera

macrodefinitii pentru:- Sortarea tablourilor

- Manipularea listelor inlantuite simplu

- Manipularea listelor dublu inlantuite

- Manipularea arborilor R-B

- Manipularea structurilor cu acces prin hash

#include "sglib.h"

Manual:http://sglib.sourceforge.net/doc/index.html

http://sourceforge.net/projects/sglib/files/sglib/


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