Thread: help using subfunctions with if/else

I'm trying to write a program that calculates the area of a square or a triangle. The program should only recognize the entries 's' or 't' (for square / triangle) and must not recognize capital letters or any other symbol.
I'm still in the very early stages of writing this and am confused.
If I understand correctly int refers to an integer, but if I ask the user to enter 's' or 't' what would I use?

This is what I have so far......


[code]
#include <iostream>
#include <string>
#include <cstdlib>
using namespace std;

void instructions(); //Instructions to the user.
void calculations(); //Calculates the area of a triangle or square.

int main ()
{
// Instructions for the user.
instructions();

// Calculates the area.
calculations();

return 0;
}

// Instructions.
void instructions()
{
cout << "This program calculates the area of "
<< "either a square or a triangle. You will" << endl;
cout << "first be asked to enter a letter "
<< "(s for square, or t for triangle) to identify" << endl;
cout << "which kind of figure you want the area computed for. "
<< "Be sure to type a " << endl;
cout << "lower-case letter, and not a capital letter. "
<< "Then you will be asked for " << endl;
cout << "dimensions of the figure. Always hit the <Enter> "
<< "key after typing whatever " << endl;
cout << "has been asked for." << endl << endl;

} // End instructions.

// Calculations.
void calculations()

{
int squ1, tri1;
float let1;
char s, t, let1;

cout << "Type the letter s to compute the area of a square, "
<< "or type t for a triangle: ";
cin >> let1 >> endl;
if (let1=s);
cout << "Enter the length of a side for the square: "
cin >> squ1;
else
if (let1=t);
cout << "Enter the length of the base for the triangle: "
cin >> tri1;
else (let1 != s, t);
cout << "This program can only recognize the "
<< "lower-case letters s and t. Sorry.: << endl;







return;
} // End calculations.

I made some changes as you suggested....

Code:

	// Calculations.
	void calculations()
	
{
	int squ1, tri1;
	float let1;  	
	char s = 's';
	char t = 't';

	cout << "Type the letter s to compute the area of a square, "
		 << "or type t for a triangle: ";
	cin >> let1;
	if (let1=='s');
		cout << "Enter the length of a side for the square: ";
		cin >> squ1;
		else
		if (let1=='t');
		cout << "Enter the length of the base for the triangle: ";
		cin >> tri1;
			else /*(let1 != s, t);*/
				cout << "This program can only recognize the "
					 << "lower-case letters s and t.  Sorry.: << endl;

	



	
	
	return;
}	// End calculations.

but I'm getting the error message

warning C4390: ';' : empty controlled statement found; is this the intent?
for "Enter the length for the side of a square:'

it's funny when I wrote it out on paper I didn't put any semi-colons, but when I typed it into the program, I did!
So much for paying attention.

Now it's telling me

error C2181: illegal else without matching if

but it looks they way we did it in class

else
if (let1=='t')

okay, I got it to run with 0 errors & 0 warnings, but even if I enter a lower-case 's' or 't' it tells me I entered a non-choice.

can anyone tell me why, please.

Code:

include <iostream>
#include <string>
#include <cstdlib>
using namespace std;

void instructions();	//Instructions to the user.
void calculations();	//Calculates the area of a triangle or square.

int main ()
{
	// Instructions for the user.
	instructions();

	// Calculates the area.
	calculations();

	return 0;
}

// Instructions.
	void instructions()
{	
	cout << "This program calculates the area of "
		 << "either a square or a triangle.  You will" << endl;
	cout << "first be asked to enter a letter " 
		 << "(s for square, or t for triangle) to identify" << endl;
	cout << "which kind of figure you want the area computed for.  "
		 << "Be sure to type a " << endl;
	cout << "lower-case letter, and not a capital letter.  "
		 << "Then you will be asked for " << endl;
	cout << "dimensions of the figure.  Always hit the <Enter> "
		 << "key after typing whatever " << endl;
	cout << "has been asked for." << endl << endl;

}  // End instructions.




	// Calculations.
	void calculations()
	
{
	int squ1, tri1;
	float let1;  	
	char s = 's';
	char t = 't';

	cout << "Type the letter s to compute the area of a square, "
		 << "or type t for a triangle: ";
	cin >> let1;
	if (let1=='s'){
		cout << "Enter the length of a side for the square: ";
		cin >> squ1;}
	else 
		if (let1=='t'){
		cout << "Enter the length of the base for the triangle: ";
		cin >> tri1;}
		else (let1 != s, t);{
			cout << "This program can only recognize the "
				 << "lower-case letters s and t.  Sorry." << endl;}

	return;
}	// End calculations.

okay, I got it to run with 0 errors & 0 warnings, but even if I enter a lower-case 's' or 't' it tells me I entered a non-choice.

can anyone tell me why, please.

Code:

include <iostream>
#include <string>
#include <cstdlib>
using namespace std;

void instructions();	//Instructions to the user.
void calculations();	//Calculates the area of a triangle or square.

int main ()
{
	// Instructions for the user.
	instructions();

	// Calculates the area.
	calculations();

	return 0;
}

// Instructions.
	void instructions()
{	
	cout << "This program calculates the area of "
		 << "either a square or a triangle.  You will" << endl;
	cout << "first be asked to enter a letter " 
		 << "(s for square, or t for triangle) to identify" << endl;
	cout << "which kind of figure you want the area computed for.  "
		 << "Be sure to type a " << endl;
	cout << "lower-case letter, and not a capital letter.  "
		 << "Then you will be asked for " << endl;
	cout << "dimensions of the figure.  Always hit the <Enter> "
		 << "key after typing whatever " << endl;
	cout << "has been asked for." << endl << endl;

}  // End instructions.




	// Calculations.
	void calculations()
	
{
	int squ1, tri1;
	float let1;  	
	char s = 's';
	char t = 't';

	cout << "Type the letter s to compute the area of a square, "
		 << "or type t for a triangle: ";
	cin >> let1;
	if (let1=='s'){
		cout << "Enter the length of a side for the square: ";
		cin >> squ1;}
	else 
		if (let1=='t'){
		cout << "Enter the length of the base for the triangle: ";
		cin >> tri1;}
		else (let1 != s, t);{
			cout << "This program can only recognize the "
				 << "lower-case letters s and t.  Sorry." << endl;}

	return;
}	// End calculations.

Why is let1 a float? If you are expecting the user to input a character, you should declare let1 as a char. This is true especially considering you comapre let1 to 's' and 't', which are both chars.

Also, JaWiB gave you two options, and it looks like you used both, but you only need one. So remove the char s = 's'; and char t = 't';

Finally - congrats on going through your program a little at a time. Its refreshing to see that you are making this work first before attempting to implement the calculations.

I changed float let1; to char let1;
but now it tells me 's' undeclared identifier and 't' undeclared identifier.

I didn't think I'd be able to do the whole program at once, so I thought I'd try to get the easier part to work then add in the math after.

Earlier you commented out the last "else if" and made it into an "else", but in your most recently posted code it looks like the comments went away. Change:

Code:

	else (let1 != s, t);{

to:

Code:

	else {

and see if that works.

And it is almost always a great idea to go a small piece at a time and get it to compile and work, even if you think you can do the whole thing at once.

Yes!!! That made it work.

Now to move on to the next part.....