如何通过引用传递创建到结构的指针数组？

Question

I need to create a program that can sum N vectors and print the final array, for example, if I put N = 2, first array (a,b) and second array(c,d) the sum should be (a+c, d+b). But I cannot compile this program, it gives an error in the

line 57 saying that it cannot convert 'float*' to 'float' into the subroutine (forca_res) arguments

PS: The quotes are into Portuguese, I'm sorry for that, but it is my native language.

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

//ESTRUTUTRA
struct vetores
{
    int dim=2;
    float *vet;
}vetor_forca,vetor_res; //Lista de Objetos


//SUBROTINA
void forca_res(float vetor_forca.vet[2], float vetor_res.vet[2])
{   
    int i;
    //Calculo do Vetor Resultante
    for(i=0;i<2;i++)
    {
        vetor_res.vet[i] = vetor_res.vet[i] + vetor_forca.vet[i];
    }
}


//PROGRAMA PRINCIPAL
int main(void)
{
    //Declaracao de variaveis
    int num, i, cont=0;
    vetores vetor_forca, vetor_res;
    vetor_forca.vet= (float*) calloc( vetor_forca.dim, sizeof(int) );
    vetor_res.vet= (float*) calloc( vetor_res.dim, sizeof(int) );

    //Leitura de dados
    printf("Digite a quantidade 'N' de vetores de forca: ");
    scanf("%d", &num);

    //Logica
    while (cont != num)
    {
        printf("\nDigite os dois elementos do vetor de forca:\n");
        for(i=0;i<2;i++)
        {
            scanf("%f", &vetor_forca.vet[i]);
        }
        //Chamando a Subrotina
        forca_res(vetor_forca.vet, vetor_res.vet);
        vetor_forca.vet= (float*) calloc( vetor_forca.dim, sizeof(int) );
        cont++;
    }
    free(vetor_forca.vet);

    //Imprimindo o Resultado
    printf("\n\nVETOR RESULTANTE:\n");
    for(i=0;i<2;i++)
    {
        printf("%f ", vetor_res.vet[i]);
    }

    //Finalizando o Programa
    printf("\n\nFim do Programa!\n");
    getch();
    return 0;
}

Answer 1

Mmm, It's been a while since I wrote C code but your syntax isn't even correct (though you didn't give the error) Your subroutine should take a

void subroutine(float* stuff, int size);

Then you treat the pointer just like an array

for I < size

Answer 2

You have other problems as well, but it looks like this might be an improved version of your function:

void forca_res(struct vetora *forca, struct vetora *res)
{
    // Set dim to be the lesser of forca->dim and res->dim
    int dim = ((forca->dim <= res->dim) ? forca->dim : res->dim);
    int i;
    //Calculo do Vetor Resultante
    for(i=0;i<dim;i++)
    {
        res->vet[i] += forca->vet[i];
    }
}

In main() , you would call it like this:

forca_res(&vetor_forca, &vetor_res);

Among other things, note that this version of the function relies on the struct vetora objects to provide the dimension of their array, instead of assuming dimension 2. Note, too, that in truth, you might want to error out if vectors of different lengths are provided as arguments, if indeed that's a case that should not arise.

Answer 3

The cause of the error message you asked about is that the specification of

void forca_res(float vetor_forca.vet[2], float vetor_res.vet[2])
{
    /* whatever */

}

is invalid. It is not possible to have names of function arguments that involve struct member access. Hence the compiler complaints.

The short fix is to remove the . characters from the argument names (both in the argument list, and within the function). In other words, use valid variable names.

There are other problems as well.