Thread: Moron Newbie needs help with errors please!

It's homework(Worth way too much of my grade) for a class (due lunch monday yayitsallmyfaultforfailing), and I'm getting errors that I can't figure out at all. Googling the names of the errors either gets me a completely useless microsoft error page, or a random forum post somewhere on the net that is so complicated I can't understand anything. Please, (benevolent internetizens) tell me what I'm doing wrong, and phrase it nice and simply. The assignment is all about pointers, and I'm supposed to shuttle numbers and letters around to make a purchasing thingy and all those uh....declared mini-program thingies at the beginning come from the assignment and I have to make them work.

Errors:

(1) : warning C4067: unexpected tokens following preprocessor directive - expected a newline
(19) : error C2100: illegal indirection
(19) : error C2664: 'GetCost' : cannot convert parameter 2 from 'double' to 'double *'
(32) : error C2447: '{' : missing function header (old-style formal list?)

Program:

Code:

#include <stdio.h>;

void Menu(char *purchase);
void GetCost(char purchase, double *item_cost);
void MoneyMenu(double *deposits, double item_cost);
int CheckMoney(double deposits, double item_cost);
void GetMoney(double *deposits, double item_cost, char purchase);
void GetChange(double *deposits, double item_cost);
void Quit(char *again);

int main()
{	
	char purchase;
	double item_cost;
	printf("Welcome to the App Store\n");
	Menu(&purchase);
	printf("%c", purchase);
	printf("%c\n", purchase);
	GetCost(purchase, *item_cost);
	printf("This item costs $%d", item_cost);
	return 0;
}

void Menu(char *purchase)
{
	printf("Products:\nG-GPS navigation $4.99\nE-Flashlight $0.99\nE-EBay autobidder $12.99\nR-Resturaunt locator $2.99\nP-Game package $9.99\n");
	scanf("%c", &purchase);
	printf("%c", purchase);
}

void GetCost(char purchase, double *item_cost);
{
	if (purchase==g)
		*item_cost='4.99';
	else
		*item_cost='5.99';
}

Also, the class is for programing in C, but the compiler is C++ 2005 express. I don't know if that matters or not, or if this is in the wrong forum. Sorry if I posted this in the wrong place.

Originally Posted by inverse9

Errors:

(1) : warning C4067: unexpected tokens following preprocessor directive - expected a newline

You shouldn't put a semicolon at the end of preprecessor directives.

Originally Posted by inverse9

(19) : error C2100: illegal indirection
(19) : error C2664: 'GetCost' : cannot convert parameter 2 from 'double' to 'double *'

This one is self explanatory if you're happy with pointers -- since you're learning about them I guess you're not

GetCost takes a char and a pointer-to-double. You need to use the & operator to take the address (i.e. get the pointer) to item_cost.

Like so

Code:

GetCost(purchase, &item_cost);

The * you had there before does the opposite of what you want -- * dereferences pointers - i.e. returns the basic type. Here's the same sentence in code: (thought you should probably look this up properly - it's important )

Code:

int myInt = 5;
int *myIntPtr = &myInt;
myint = *myIntPtr;

Originally Posted by inverse9

(32) : error C2447: '{' : missing function header (old-style formal list?)

You have another extraneous semicolon after the declaration of GetCost(). This means that the compiler interprets it as a function prototype (fine) but then the braced-block following it is illegal.

Originally Posted by quzah

Turn on your compiler warnings, and it should be telling you that the printf line is wrong. You are printing a memory address, not the value at that address.


Quzah.

The only warning I get is about how using scanf is unsafe. And yes, I can't seem to find my memory. Please someone tell me how I'm supposed to do the super-simple write things in memory here and from somewhere else retrieve that thingy, since my class notes, paperweight book, and google are conspiring to make me feel stupid. I made the title "Moron newbie" for a reason, since from your actually-experienced programer viewpoints I'm a total idiot.

Quite a few of your scanfs and printfs have the wrong level of indirection in them.

Code:

void Menu(char *purchase)
{
	printf("Products:\nG-GPS navigation $4.99\nE-Flashlight $0.99\nE-EBay autobidder $12.99\n");
	printf("R-Resturaunt locator $2.99\nP-Game package $9.99\nPlease enter a selection:");
        // this is wrong. Scanf expects a pointer to some memory. purchase is a pointer, so you don't need the & here. Using & makes the type char**.
        scanf("%c", &purchase);
       // also wrong -- should use * to dereference the pointer here.
	printf("%c", purchase);//This prints the letter I enter.
}

Code:

printf("%f", item_cost); //This gives me 0.000000 :( Hey, green smilies work! :D Awesome.

quzah mentioned this, you should dereference item_cost. I couldn't get MSVC to give a warning about this either. I don't know if I'd expect it to... since C isn't very strict about types and pointers can be interpreted as integral types (addresses). Don't know. IT'd be nice!

Last problem, this one you might kick yourself for:

Code:

void GetCost(char purchase, double *item_cost)
{
	if (purchase=='g')
                /* item_cost is a double, so you should not have single quotes around the 4.99. You should have no quotes, like *item_cost=4.99; */
		*item_cost='4.99';
	else
                /* Same here */
		*item_cost='5.99';
	printf("%f", item_cost); //This gives me 0.000000 :( Hey, green smilies work! :D Awesome.
}

*Head explodes with befuddlement/gratitude*

Well, I thought I had to do some arcane things to the declarations, but everything works and more importantly I think I kinda understand how this stuff works now. Thanks!

(50/50 chance I'm gonna be back here in half an hour.)

Originally Posted by inverse9

*Head explodes with befuddlement/gratitude*

Well, I thought I had to do some arcane things to the declarations, but everything works and more importantly I think I kinda understand how this stuff works now. Thanks!

Excellent, glad it's working! It does become natural eventually, honest I think I became happier about it all when I mentally substituted the word "pointer" for "address". The fact that pointers are typed makes this slightly incorrect, but in general it seemed easier to swallow - and it's easier to remember where you should dereference and where you shouldn't. You're certainly not an idiot/moron for not nailing them the first time through.

(50/50 chance I'm gonna be back here in half an hour.)

good luck!