C Returning an array from a function -


and having trouble grasping arrays in c , how return them via function. if 

int main() {      int num_set[10]={0,1}; //initialize first 2 elements 0,1 , rest 0      int* p=num_set;             //assign array int pointer called p      printf("\n%i",&num_set);    //outputs 2686660 on machine      printf("\n%i",&num_set[0]); //also outputs 2686660      printf("\n%i",p);           //also outputs 2686660      printf("\n%i",p[1]);*       //outputs 0; same num_set[1]  }

it works expected, when try return array through function following 

int multiply_by_2(int given_number) {      int num_set[10];      for(int fun_counter=0; fun_counter<10; fun_counter++)      {           num_set[fun_counter] = (given_number*2) ;      }      return num_set;  //return int array num_set caller }  int main() {      int* p = multiply_by_2(300)    //assign array returned function p      for(int main_counter=0; main_counter>10; main_counter++)      {           printf("\np[%i] = %i"                  , i, p[i]);      } }

i error saying "invalid conversion 'int' 'int*'"

they no error when assigned array int pointer in first code, error when try return through function.

please help.

there number of errors here.

  1. the return type of function multiply_by_2 needs int* - i.e pointer integer. returned pointer first element of array.

  2. you attempting return variable initialized on stack (num_set). disappear multiply_by_two function exits, because automatic variable. instead, should use malloc function allocate heap memory. here's link explaining difference between stack , heap memory

  3. you have > should have < in for loop in main. written loop exit.

  4. minor point - number 10 repeated several times throughout code. better practice use variable or #define give number meaningful name

here's amended version of code:

#include <stdio.h> #include <stdlib.h> //this required use malloc  #define array_size 10  int* multiply_by_2(int given_number) {     int *num_set =malloc(sizeof(int)*array_size);     for(int fun_counter=0; fun_counter<array_size; fun_counter++)     {         num_set[fun_counter] = (given_number*2) ;     }     return num_set;  //return int array num_set caller }  int main() {     int* p = multiply_by_2(300);    //assign array returned function p     for(int i=0; i<array_size; i++)     {          printf("\np[%i] = %i", i, p[i]);     }     free(p); }

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