Thread: Help with chained lists

hello everyone
i have to do a "text editor" or at least something that types lol
im learning pointers and we have to make this using lots of pointers
and it has to be in C so no <string.h> or any other headers like that

but so far i have a problem

before you look at the code
the part that doesnt work is this function
void add_char( struct c_string **p_str, char letra );


this is a simpler veersion of my code some parts are not in it

Code:

#include <stdio.h>
#include <windows.h>
#include <ctype.h>
#define front 2

struct c_string
{
    struct c_string *ant;
    char letra;
    struct c_string *prox;
};

struct tp_lin
{
    struct tp_lin *ant;
    int nro;
    struct c_string  *inicio;
    struct tp_lin *prox;
};

void init_text( struct tp_lin **p_lin )
{
    p_lin = NULL;
}

void add_lin( struct tp_lin **p_lin )
{
    struct tp_lin *nova, *aux;
    if( *p_lin == NULL )
    {
        nova = (struct tp_lin*) malloc(sizeof(struct tp_lin));
        nova->ant = NULL; 
        nova->nro = 0;
        nova->inicio = NULL;
        nova->prox = NULL;
        *p_lin = nova;          
    }
    else
    {
        aux = *p_lin;
        while( aux->prox != NULL )
            aux = aux->prox;
        nova = (struct tp_lin*) malloc(sizeof(struct tp_lin));
        nova->ant = aux;
        nova->nro = 0;
        nova->inicio = NULL;
        nova->prox = NULL;
        aux->prox = nova;
    }
}

//BAD FUNCTION
void add_char( struct c_string **p_str, char letra )
{
    struct c_string *nova, *aux;
    if( *p_str = NULL )
    {
        nova = (struct c_string*) malloc(sizeof(struct c_string));
        nova->ant = NULL;
        nova->letra = letra;
        nova->prox = NULL;
        *p_str = nova;
    }
    else
    {
        aux = *p_str;
        while( aux->prox != NULL )
            aux = aux->prox;
        nova = (struct c_string*) malloc(sizeof(struct c_string));
        nova->ant = aux;
        nova->letra = letra;
        nova->prox = NULL;
        aux->prox = nova;
    }
}

int main()
{
    struct tp_lin *p_ini;
    struct tp_lin *p_lin;
    struct c_string *p_cur;
    char chOpt, chOpt2;
    
    init_text( &p_ini );    // Inicializa o ponteiro p/ NULL 
 
    do
    {
        chOpt = getch();
        if( chOpt == 0 )
            chOpt2 = getch();
        if( isalpha( chOpt ) )  
        {   

            if( p_ini == NULL ) 
            {
                add_lin( &p_ini );   
                p_lin = p_ini; 
                add_char( &p_lin->inicio, chOpt );  // THIS IS WHERE MY PROBLEM IS 
                p_cur = p_lin->inicio;  
            }
            /*else 
            {
                add_char( p_lin->inicio, chOpt );        
            }*/
            printf("%c",p_cur->letra);
        }
        
    }while( chOpt != 27 );

return 0;
}

if your willing to help me but need more info
just tell me what you want to know

and thanks a lot in advanced

What does "doesn't work" mean?


Quzah.