CS50 Pset 2：可读性

Question

I'm having issues returning the string as an integer through printf. Heres the error i keep getting, but if I just %i to %s it compiles and prints text. i need to print the number of letters in a string, not the actual text itself.

readability.c:20:20: error: format specifies type 'int' but the argument has type 'string' (aka 'char *') [-Werror,-Wformat] printf("%i\n", text); ~~ ^~~~ %s

my count_letters function seems to work okay but I'm sure I have a mistake somewhere that I'm missing. code here:

#include <cs50.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>

int count_letters(string text);

int main(void)
{
    // provides text: statement
    printf("Text:");

    // gets string from user
    string text = get_string(" ");

    // should count amount of letters and skip spaces and punctutation
    int count_letters(string text);

    // prints number of characters in int form
    printf("%i\n", text);
}
int count_letters(string text)
{
    int letters = 0;
    int i;

    for (i = 0; letters < strlen(text); i++)
    {
        if isalpha(text[i])
        {
            letters++;
        }
    }
    return letters;
}

Answer 1

I don't know where the cs50 header comes from but I assume it's from a course. I can see two problems:

1. int count_letters(string text); in main:

Here:

// should count amount of letters and skip spaces and punctutation
    int count_letters(string text);

You redeclare the function instead of using it and getting it's return value, use something like int result=count_letters(text); instead.

2. The printf itself

Here:

// prints number of characters in int form
    printf("%i\n", text);

You pass text which is a string (type char*) but %i (or %d) requires an integer, you can (and should) use the return value of the previous function in this case: so something like printf("%i\n", result); if you made the modification I suggested in 1).

Otherwise in standard c (please keep in mind I kept it simple and tried to do something similar to your code so there are missing error checking):

#include <stdio.h>
#include <string.h>
#include <ctype.h>

int count_letters(char* text);

int main(void)
{
    // provides text: statement
    printf("Text:");

    // gets string from user with size 14 (+1 for \0)
    char text[15];
    scanf("%14s", text); 

    // should count amount of letters and skip spaces and punctutation
    int result=count_letters(text);

    // prints number of characters in int form
    printf("%i\n", result);
}

int count_letters(char* text)
{
    int letters = 0;
    int i;

    for (i = 0; letters < strlen(text); i++)
    {
        if isalpha(text[i])
        {
            letters++;
        }
    }
    return letters;
}