How to turn into a tiny value of a struct?

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The next function should turn variables into lowercase and then compare them. I’ve tried converting before, but also bugged. Arithmetic use of pointers together with variables of a struct. Pointer points to the struct.

How to fix the error present in the following code snippet:

struct registro{ 
    char conta[50], senha[50], usuario[50];
}atual[1000], *ptr;

int verifica_usuario(int *ptr){
    int i;
    for(i = 0; i < *ptr; i++) {
        if(strcmp(tolower(atual[*ptr].usuario), tolower(atual[i].usuario)) == 0) {
                return 0;
        }
    }
    return 1;
}
c array string pointer struct

  • "Arithmetic pointer use" no, you do not use pointer arithmetic. You use a simple positional vector access atual. And also pass int *ptr as argument seems quite unnecessary for the use being made of it

  • Yes, yes. My goal follows this conviction, I want the program to classify "NAME" == "name", hence the tolower. the program receives an entry in which it asks for a user name, but this name cannot already be registered, even if there is divergence between upper and lower case.

  • 2

    tolower receives a char and returns a char, so it makes no sense to call for a char char[] or char*. atual.usuario is of what type ?

  • It’s kind of char, too.

  • Put the definition of struct in the question, so that it is evident to anyone who wants to answer

  • What Isac meant was, how’s the code of struct between the word recervada struct, your key opener { and their respective key closes } with all field definitions and their respective names

  • What are you calling your role in main ?

  • verific = verifica_account(&v);

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1 answer

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Although there are insensitive functions, it is not part of the standard. To run anywhere create your own function:

#include <stdio.h>
#include <ctype.h>
 
int stricmp(char const *s1, char const *s2) {
   while (1) {
        int res = tolower(*s1) - tolower(*s2);
        if (res != 0 || !*s1) return res;
        s1++;
        s2++;
    }
}
 
int main(void) {
    printf("%d\n", stricmp("aaa", "AAA"));
    printf("%d\n", stricmp("aaa", "aaa"));
    printf("%d\n", stricmp("aaa", "AAB"));
    printf("%d\n", stricmp("abb", "AAB"));
}

Behold working in the ideone. And in the repl it.. Also put on the Github for future reference.

Then check the member of the structure I think you already know. Follow the recommendations of the comments, the algorithm is more complicated than it should be. And there are other mistakes in it, but that’s another problem.

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