How to pass a list of pointers that references functions as a parameter

Question

I have a list of pointers that refer to functions in my code and I need to pass this list as a parameter to a function that prints the cases:

double f00(double x){
  ...
  return x;
}

double f01(double x){
  ...
  return x;
}

void imprimeTeste(int tam, double** ptrsToFunc(?), char** strings){ //Como receber corretamento
  for(int i = tam; i < tam; i++){
    int result = takeRoot(ptrsToFunc[i]);
    printf("%s resultado %d", strings[i], result);
  }
}

int main() {
  char* strings[2] = {"Função 1", "Função 2"};
  double (*ptrsToFunc[2])(double) = {f00, f01};
  imprimeTeste(2, pntsToFunc, strings);
}

Notice that I can pass to my function to char* strings[2] and receive as char** strings, but I don’t know how to mount the header of my function imprimeTeste to receive the list double (*ptrsToFunc)(double).

Answer 1

See these examples:

Case 1: using a pointer vector and size

Declare the vector thus:

    double (*ptrs[])(double) = {f00, f01};

And in function so:

void Teste1(int,double (*[])(double));

note that you can already list the function names in the statement, if it is something constant.

a full test

#include <stdio.h>
#include <stdlib.h>

double f00(double);
double f01(double);
void Teste1(int,double (*[])(double));

int main(void)
{
    double (*ptrs[])(double) = {f00, f01};
    Teste1(2, ptrs);
    return 0;
}

double f00(double x)
{
    printf("F0(%.1f) chamada\n", x);
    return 42.0;
}

double f01(double x)
{
    printf("F1(%.1f) chamada\n", x);
    return 42.1;
}

void Teste1(int tam, double (*F[])(double))
{
    printf("%d funcoes a chamar\n", tam);
    for (int i = 0; i < tam; i += 1)
        printf("Funcao %d retornou %.1f\n", i, F[i]((double)i));
}

exit

2 funcoes a chamar
F0(0.0) chamada
Funcao 0 retornou 42.0
F1(1.0) chamada
Funcao 1 retornou 42.1

Case 2: a pointer vector, NULL-terminated

It can be useful when it will always process all the records, in order, as a batch.

It’s simpler to use one typedef, something like that:

typedef double (*Fd_d)(double);

And declare the function with him

void Teste2(Fd_d*);`

In this case you have to mount the vector, as the system does with main() and the vector of arguments:

    Fd_d* vetor = (Fd_d*)malloc(3 * sizeof(Fd_d));
    vetor[0]    = f00;
    vetor[1]    = f01;
    vetor[2]    = NULL;
    Teste2(vetor);

A complete example

#include <stdio.h>
#include <stdlib.h>

double f00(double);
double f01(double);

typedef double (*Fd_d)(double);
void Teste2(Fd_d*);

int main(void)
{
    printf("\nUsando vetor de ponteiros\n\n");
    Fd_d* vetor = (Fd_d*)malloc(3 * sizeof(Fd_d));
    vetor[0]    = f00;
    vetor[1]    = f01;
    vetor[2]    = NULL;
    Teste2(vetor);
    return 0;
}

double f00(double x)
{
    printf("F0(%.1f) chamada\n", x);
    return 42.0;
}

double f01(double x)
{
    printf("F1(%.1f) chamada\n", x);
    return 42.1;
}

void Teste2(Fd_d* vetor)
{
    int i = 0;
    while (vetor[i] != NULL)
        printf("Funcao %d retornou %.1f\n", i, vetor[i]((double)i)), i ++;
}

Departure from the example

Usando vetor de ponteiros

F0(0.0) chamada
Funcao 0 retornou 42.0
F1(1.0) chamada
Funcao 1 retornou 42.1