How do I properly call the function I created to the main?

Question

So I suck with functions and need to debug this. Im pretty sure the function ToPigLating does its job well at converting. However I just need help calling the function ToPigLatin inside of my main function. But when I try doing that I just get a bunch of error codes.

#include <stdlib.h>
#include <string.h>

#define LEN 32

char* ToPigLatin(char* word[LEN]){
    char word[LEN];
    char translation [LEN];
    char temp [LEN];
    
    int i, j;
    
    
    while ((scanf ("%s", word)) != '\0') {
        strcpy (translation, word);
        
        //just pretend I have all the work to convert it in here. 
    } // while
}

int main(){
    printf("Enter 5 words: ");
    scanf("%s", word);
    ToPigLatin();
    
    
}```

Answer 1

Roughly, variables only exist within the function they're declared in. The word in ToPigLatin exists only within ToPigLatin. It is not available in main. This lets us write functions without worrying about all the rest of the code.

You need to declare a different variable in main, it can also be called word, to store the input and then pass that into ToPigLatin.

Let's illustrate with something simpler, a function which doubles its input.

int times_two(int number) {
  return number * 2;
}

We need to give times_two a number.

int main() {
  // This is different from "number" in times_two.
  int number = 42;

  // We have to pass its value into time_two.
  int doubled = times_two(number);

  printf("%d doubled is %d\n", number, doubled);
}

---

Your case is a bit more complicated because you're working with input and memory allocation and arrays. I'd suggest just focusing on arrays and function calls for now. No scanf. No strcpy.

For example, here's a function to print an array of words.

#include <stdio.h>

// Arrays in C don't store their size, the size must be given.
void printWords(const char *words[], size_t num_words) {
    for( int i = 0; i < num_words; i++ ) {
        printf("word[%d] is %s.\n", i, words[i]);
    }
}

int main(){
    // This "words" variable is distinct from the one in printWords.
    const char *words[] = {"up", "down", "left", "right"};
    
    // It must be passed into printWords along with its size.
    printWords(words, 4);
}

Answer 2

ToPigLatingToPigLating function expects to have a parameter like ToPigLating("MyParameter");

Answer 3

Hello there icecolddash.

First things first, there are some concepts missing. In main section:

scanf("%s", word);

You're probably trying to read a string format and store in word variable. In this case, you should have it on your declaration scope. After some adjustment, it will look like this:

int main(){
char word[LEN];

As you defined LEN with 32 bytes maximum, your program will not be allowed to read bigger strings. You're also using standard input and output funcitions as printf, and so you should ever include stdio.h, thats the header which cointains those prototypes already declared, avoiding 'implicit declaration' compiling warnings.

Next issue is how you're declaring your translation function, so we have to think about it:

char* ToPigLatin(char* word[LEN])

In this case, what you wrote: ToPigLatin is a funcion that returns a char pointer, which means you want your function to probably return a string. If it makes sense to you, no problem at all. Although we got some real problem with the parameter char* word[LEN].

Declaring your variable like this, assume that you're passing an array of strings as a parameter. If I got it right, you want to read all five words in main section and translate each one of them. In this case I suggest some changes in main function, for example :

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

#define LEN 32
#define MAX_WORDS 5

char *globalname = "translated";

char* ToPigLatin(char* word){
  char *translation = NULL;
  //Translation work here.
  if ( !strcmp(word, "icecolddash") ){
    return NULL;
  }
  
  translation = globalname;

  return translation;
}

int main(){
  char word[LEN];
  char *translatedword;
  int i;
  printf("Enter 5 words: \n");
  for ( i=0; i < MAX_WORDS; i++ ){
    fgets(word, sizeof(word), stdin);
    strtok(word, "\n"); // Just in case you're using a keyboard as input.
    translatedword = ToPigLatin(word);  
    if ( translatedword != NULL ){
      //Do something with your translation
      //I'll just print it out as an example
      printf("%s\n", translatedword);
      continue;
    }
    
    // Generic couldn't translate message
    printf("Sorry, I know nothing about %s\n", word);
    
  }
  return 0;
}

The above code translate every word in a fixed word "translated". In case of reading the exact input "icecolddash", the program will output a generic error message, simulating some problem on translation process.

I hope this help you out with your studies.

Answer 4

There are a few things that I see.

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

char* ToPigLatin(char* word){
    printf(word);
    return word;
}

int main(){
    printf("Enter 5 words: ");
    
    // declare the variable read into by scanf
    char * word = NULL;
    
    scanf("%s", word);
    
    //Pass the variable into the function
    ToPigLatin(word);
    
    // Make sure you return an int from main()
    return 0;
}

I left some comments in the code with some specific details.

However, the main thing that I would like to call out is the style of the way you're writing your code. Always try to write small, testable chunks and build your way up slowly. Try to get your code to compile. ALWAYS. If you can't run your code, you can't test it to figure out what you need to do.

As for the char ** comment you left on lewis's post, here is some reading you may find useful in building up your intuition:

https://www.tutorialspoint.com/what-does-dereferencing-a-pointer-mean-in-c-cplusplus

Happy coding!