confused...integer compared to pointer?

[nzer]

Hi,

I thought i'd have a play around in C++. I'm a complete newbie (in C++ not programming). I'm trying to make a simple calculator to get a grasp of the syntax. (i'm used to python and VB).

What trying to do is declare the functions with prototype functions up the top. Get from the user if they want to do addition,subtracton,div or multi and then do it. This is where my first problem comes in. I don't understand how to do.. elifs.. or elseifs.. if c++ even does it?. And also I don't know how to compare properly using the logical operator || .. It keeps giving me the error ANSI C++ forbids comparison between pointer and integer. I'll post the gcc output and my attempt to do the program.

Thanks very much for any help!

#include <iostream>
// Simple add, subtract, mult,divide calculator

int funcAdd(int,int);
int funcSub(int,int);
float funcDiv(int,int);
long funcMulti(int,int);

int main()
{
    char decide;
    int first;
    int second;
    int result;
    
    std::cout << "What would you like to do: (A)dd, (S)ubtract, (D)ivide or (M)ultiply ?\n";
    std::cin >> decide;
    
    if ( (decide == "A") || (decide == "a") || (decide == "S") || (decide = "s") || (decide == "D") || (decide == "d") || (decide == "M") || (decide == "m") )
    {
	if ((decide == "A") || (decide == "a"))
	    std::cout << "\nAddition\n";
	    std::cout << "\nEnter the first number:";
	    std::cin >> first;
	    std::cout << "\nEnter the second number:";
	    std::cin >> second;
	    result = funcAdd(first,second);
	    std::cout << "\nAnswer for " << first << " + " << second << " = " << result << std::endl;
	else
	if ( (decide == "S") || (decide = "s") )
	    std::cout << "\nSubtraction\n";
	    std::cout << "\nEnter the first number:";
	    std::cin >> first;
	    std::cout << "\nEnter the second number:";
	    std::cin >> second;
	    result = funcSub(first,second);
	    std::cout << "\nAnswer for " << first << " - " << second << " = " << result << std::endl;
	else
	if ( (decide == "D") || (decide == "d")	)
	    std::cout << "\nDivision\n";
	    std::cout << "\nEnter the first number:";
	    std::cin >> first;
	    std::cout << "\nEnter the second number:";
	    std::cin >> second;
	    result = funcDiv(first,second);
	    std::cout << "\nAnswer for " << first << " / " << second << " = " << result << std::endl;
	else
	if ( (decide == "M") || (decide == "m")	)
	    std::cout << "\nMultiplication\n";
	    std::cout << "\nEnter the first number:";
	    std::cin >> first;
	    std::cout << "\nEnter the second number:";
	    std::cin >> second;
	    result = funcMulti(first,second);
	    std::cout << "\nAnswer for " << first << " * " << second << " = " << result << std::endl;
    }
    else
	std::cout "\n You did not enter a valid option";
}

int funcAdd(int x,int y)
{
    return x + y;
}

int funcSub(int x, int y)
{
    return x - y;
}

float funcDiv(int x, int y)
{
    return x / y;
}

long funcMulti(int x, int y)
{
    return x * y;
}

andrew@me:~$ g++ calc.cpp -o calc 
calc.cpp: In function `int main()':
calc.cpp:19: ANSI C++ forbids comparison between pointer and integer
calc.cpp:19: ANSI C++ forbids comparison between pointer and integer
calc.cpp:19: ANSI C++ forbids comparison between pointer and integer
calc.cpp:19: assignment to `char' from `const char *' lacks a cast
calc.cpp:19: ANSI C++ forbids comparison between pointer and integer
calc.cpp:19: ANSI C++ forbids comparison between pointer and integer
calc.cpp:19: ANSI C++ forbids comparison between pointer and integer
calc.cpp:19: ANSI C++ forbids comparison between pointer and integer
calc.cpp:21: ANSI C++ forbids comparison between pointer and integer
calc.cpp:21: ANSI C++ forbids comparison between pointer and integer
calc.cpp:29: parse error before `else'
calc.cpp:38: parse error before `else'
calc.cpp:45: warning: assignment to `int' from `float'
calc.cpp:47: parse error before `else'
calc.cpp:58: parse error before string constant
calc.cpp:59: confused by earlier errors, bailing out

[CornedBee]

First off, you can avoid having to type std:: all the time by adding
using namespace std;
directly after the includes.

There is no elseif or elif in C++. else if works the same.

The "can't compare" errors stem from the fact that in C++ "h" is a c-style string (a pointer to a character) while 'h' is the actual character h.

Also your program would be better structured with a switch statement:

std::cin >> decide;
switch(decide)
{
case 'A':
case 'a':
  // ...
  break;
case 'S':
case 's':
  // ...
  break;
// ...
default:
  cout << "\n You did not enter a valid option";
  break;
}

[nzer]

thanks for the help!

.. i see so lose the "" when dealing with strings in c++ then?

so.. the switch thing works like this..?

switch(variable)
{
case: //condition one
//statements
break;
case: //condition x
//statements
break;
//more case and statements
default:
//returns anything that is not true in the switch
}

Again, thanks

[Comreak]

Yep, that's how it works. Personally, I like it better than vbs select case. What do you think nzer?

[nzer]

This, it works in linux :-)

[CornedBee]

Should work in windows too, I see no platform specifics in the code.

[nzer]

sorry .. lol.. i read that as "i like vbs select case better" .. so i thought you were saying you preferred VB.. so.. i agree with you then.. switch is much nicer :-)

merry xmas .. hey i'm one of the first to see the sun on xmas how amazing.. sort of

[PT Exorcist]

and instead of having || for A and a but it to lower case

[nzer]

you mean A && a .. doesn't that require both sides of the statement to be true though? i.e it must = 'A' and 'a'