Thread: Passing in values to functions

is it possible to instead send a string to the function as well

The C language does not support sending/returning arrays by value, but you may pass them in by reference - i.e. A pointer to the first char in the array

And sometimes I want to call this function without the int being called

If you are referring to overloading the function, the answer is no. What you can do is use a pointer to pass the int into the function and when you want to not use the int pass a NULL into the function -> Your function could test for this and behave differently if the int was a NULL pointer

Originally Posted by Mentallic

Oh I see. Is that how some common library functions such as printf and scanf work?

They use a "variable argument list" using the macros defined in stdarg.h. That might be what you want, but you'd have to explain exactly what you're trying to accomplish to get the best advice.

Entering a NULL pointer to printf is a big no.

If you are interested in the way they work, look up "va_list"/ "va_start"/ "va_end".

Originally Posted by Mentallic

Well, each node in my linked list is a line of text, and I'm required to - depending on user input - print out either a specific line number (hence the int lineNumber) or also if they input '+' or '-' to print out the next/previous line respectively.

Here are some possibilities.


Use negative line numbers as special codes:

Code:

#define CMD_NEXT -1
#define CMD_PREV -2

void print(Line *head, int lineNumber) {
    switch (lineNumber) {
    case CMD_NEXT:
        // print next line
        break;
    case CMD_PREV:
        // print prev line
        break;
    default:
        if (lineNumber > 0)  // or >= 0
            // print line lineNumber
        else
            // error
    }
}

// calls
print(line, 20);         // print line 20
print(line, CMD_NEXT);   // print next line
print(line, CMD_PREV);   // print prev line

Use an extra parameter:

Code:

void print(Line *head, char command, int lineNumber) {
    switch (command) {
    case 'N':
        // print next line
        break;
    case 'P':
        // print prev line
        break;
    case 'L':
        // print line lineNumber
        break;
    default:
        // error
    }
}

// calls
print(line, 'L', 20); // print line 20
print(line, 'N', 0);   // print next line
print(line, 'P', 0);   // print prev line

Use a string:

Code:

void print(Line *head, char *command) {
    int lineNumber;
    switch (command[0]) {
    case 'N':
        // print next line
        break;
    case 'P':
        // print prev line
        break;
    case 'L':
        // print line lineNumber
        lineNumber = atoi(command + 1);
        break;
    default:
        // error
    }
}

// calls
print(line, "L20"); // print line 20
print(line, "N");   // print next line
print(line, "P");   // print prev line