Programming Forums > Application Development > C++

meverha1 · Sep 10th, 2005, 1:03 PM

Just a couple of simple function questions relating to a simple program exercise from a book. I'm trying to write a program to calculate BMI (Body/mass index) and am writing each calculation as a simple function.

1) Does "main()" have to be the first function listed in a program or can I define my functions then "main()"

2) Is it a good idea to create a function for each computation/formula? I know that for a simple operation like this I am making things overly complex but I want to get into the habit of creating functions, if that's proper form.

BinaryStorm · Sep 10th, 2005, 1:18 PM

1.
main doesn't need to be first, but if you declare other functions after main, and wish to use them in main(), you need to make prototypes.
example :

(Toggle Plain Text)

// prototype
int function1 (int a, int b); // note the semicolon

int main()
{
    int a = function1 (423, 36);
    return 0;
}

// function
int function1 (int a, int b)
{
    return a*b;
}

2. Yes.
example:
What if you wish to return sum and product of parameters sent to function?
you can't do this :

(Toggle Plain Text)

...
return n1+n2;
return n1*n2;

Each function should do only one thing, so your program will be more readable, and one step closer to bug-free code.

coldDeath · Sep 10th, 2005, 1:19 PM

1) It does not need to be the first function.

2)I think you should have one function, but you can do what you like.
Here is an example of what you could do:

(Toggle Plain Text)

int calculate(int bodymass)
{
//calculate the bodymass or whatever it does
//cout the answer 
}

Then in the main function you can cin the bodymass or whatever you need and then it calls that function.

Sorry if that didn't make sense because i dont really know what formula you would use to find the BMI.

EDIT: If you tell me the forumla i would write out the a working example, but i think you might want to do it yourself because you seem keen to learn.

EDIT EDIT: grrr binaryStorm beat me

DaWei · Sep 10th, 2005, 1:22 PM

It is a good idea to modularize your program for comprehension and maintenance purposes. It is a good idea to examine your application for objects and design them. Functions then become methods of these objects, when appropriate. Wheels and carburetors are objects; friction and air flow are variables; explosions and calculations are procedural functions that might well serve as methods.

Shapeless · Sep 10th, 2005, 5:17 PM

Quote:

Originally Posted by coldDeath

1)

(Toggle Plain Text)

int calculate(int bodymass)
{
//calculate the bodymass or whatever it does
//cout the answer 
}

Well, bad idea. One function has only one job todo.your function "calculate" calculates and prints the output. And so return and do not show "the answer".

meverha1 · Sep 11th, 2005, 10:38 AM

So, I set up my program but when I complile I get the error "too few arguments to function" since I'm new to C++ I have no idea what this means. Can someone point me in the right direction? I'm not looking for someone to right the program for me, just help me correct what I have and explain what I did wrong.

Code is below.

(Toggle Plain Text)

// Programming exercise 3.2 - figuring BMI
#include <iostream>
using namespace std;

double weightconversion(double); 
double feettoinches(double);
double inchestometers(double);
double bmicalc(double);


	const int feet_inches = 12;
	const double inches_meters = 0.0254;
	const double lbs_kilos = 2.2;
	
	int weight_lbs = 0;
	int height_feet = 0;
	int height_inches = 0;
	double weight_kilos = 0.0;
	double height_meters = 0.0;
	double heightininches = 0;
	double bmi = 0.0;

int main()
{
	cout << "Enter your weight: ";  // User input values 
	cin >> weight_lbs;
	cout << endl
            << "Enter your height in feet and inches: ";
    cin >> height_feet >> height_inches;
    
    weight_kilos = weightconversion(weight_lbs);
    heightininches = feettoinches();
    height_meters = inchestometers(heightininches);
    bmi = bmicalc();
    
    cout << endl
         << "Your BMI is: "
         << bmi
         << endl;
         
    system("PAUSE");
    return 0;  
         
    
}

double weightconversion(double)    // Function for conversion of weight
{
	weight_kilos = weight_lbs * lbs_kilos;
	return weight_kilos;
}

int feettoinches()           // Function for conversion of height to inches
{
    heightininches = (height_feet * feet_inches) + height_inches;
    return heightininches;
}

double inchestometers(double)   // Function for conversion inches to meters
{
       height_meters = heightininches * 0.0254;
       return height_meters;
}

double bmicalc()      // Function to calculate BMI
{
       bmi = weight_kilos * (height_meters * height_meters);
       return bmi;
}

coldDeath · Sep 11th, 2005, 10:44 AM

Too few arguments means that you created a function and when you called it you didnt use the right amount of arguments.
example:

(Toggle Plain Text)

//simple function
int multiply (int a, int b)
{
    int sum;
    sum = a * b;
    return sum;
}



//pretend this is where you want to call the function.
multiply(2,3);
//that would give you the answer 6

//but if you call it like this:
multiply(6);
//it will say: too few arguments, because you only supplied one and the function needs two.

Hope i have helped.

meverha1 · Sep 11th, 2005, 10:53 AM

So I can't do something like this:

(Toggle Plain Text)

...

double function1(double);

...

double function1()
{
...
}

Basically, I delclare a function at the beginning of the program and then use it later with empty brackets, like I could "main()"?

coldDeath · Sep 11th, 2005, 10:59 AM

nono.
You make you function first.

(Toggle Plain Text)

double function1(){
...
}

Then in the main() function you call it like this:

(Toggle Plain Text)

funtion1();

You only write stuff inbetween the ( and ) (when making a function) when you want an argument to the function.

meverha1 · Sep 11th, 2005, 11:04 AM

Ok, I think I corrected it. Basically when I called the functions in "main()" I had to do this:

(Toggle Plain Text)

weight_kilos = weightconversion(weight_lbs);

What I was originally trying to do was this:

(Toggle Plain Text)

weight_kilos = weightconversion();

So, when I call a function in main I always have to assign some sort of value to it between "()"?

Sep 10th, 2005, 1:03 PM	#1
meverha1 Newbie Join Date: Sep 2005 Posts: 11 Rep Power: 0	Simple Function Questions Just a couple of simple function questions relating to a simple program exercise from a book. I'm trying to write a program to calculate BMI (Body/mass index) and am writing each calculation as a simple function. 1) Does "main()" have to be the first function listed in a program or can I define my functions then "main()" 2) Is it a good idea to create a function for each computation/formula? I know that for a simple operation like this I am making things overly complex but I want to get into the habit of creating functions, if that's proper form.

Sep 10th, 2005, 1:18 PM	#2
BinaryStorm Programmer Join Date: Sep 2005 Location: Po�ega, Croatia Posts: 93 Rep Power: 4	1. main doesn't need to be first, but if you declare other functions after main, and wish to use them in main(), you need to make prototypes. example : (Toggle Plain Text) // prototype int function1 (int a, int b); // note the semicolon int main() { int a = function1 (423, 36); return 0; } // function int function1 (int a, int b) { return ab; } // prototype int function1 (int a, int b); // note the semicolon int main() { int a = function1 (423, 36); return 0; } // function int function1 (int a, int b) { return ab; } 2. Yes. example: What if you wish to return sum and product of parameters sent to function? you can't do this : (Toggle Plain Text) ... return n1+n2; return n1n2; ... return n1+n2; return n1n2; Each function should do only one thing, so your program will be more readable, and one step closer to bug-free code.

Sep 10th, 2005, 1:19 PM	#3
coldDeath Expert Programmer Join Date: Aug 2005 Location: UK Posts: 862 Rep Power: 4	1) It does not need to be the first function. 2)I think you should have one function, but you can do what you like. Here is an example of what you could do: (Toggle Plain Text) int calculate(int bodymass) { //calculate the bodymass or whatever it does //cout the answer } int calculate(int bodymass) { //calculate the bodymass or whatever it does //cout the answer } Then in the main function you can cin the bodymass or whatever you need and then it calls that function. Sorry if that didn't make sense because i dont really know what formula you would use to find the BMI. EDIT: If you tell me the forumla i would write out the a working example, but i think you might want to do it yourself because you seem keen to learn. EDIT EDIT: grrr binaryStorm beat me __________________ Programming Tutorials - Linux Installation Guide - Learn Python - Learn C++ Got Slack? Join us at #programmingforums @ irc.freenode.net! My software never has bugs. It just develops random features.

Sep 10th, 2005, 1:22 PM	#4
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	It is a good idea to modularize your program for comprehension and maintenance purposes. It is a good idea to examine your application for objects and design them. Functions then become methods of these objects, when appropriate. Wheels and carburetors are objects; friction and air flow are variables; explosions and calculations are procedural functions that might well serve as methods. __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Sep 11th, 2005, 10:38 AM	#6
meverha1 Newbie Join Date: Sep 2005 Posts: 11 Rep Power: 0	So, I set up my program but when I complile I get the error "too few arguments to function" since I'm new to C++ I have no idea what this means. Can someone point me in the right direction? I'm not looking for someone to right the program for me, just help me correct what I have and explain what I did wrong. Code is below. (Toggle Plain Text) // Programming exercise 3.2 - figuring BMI #include <iostream> using namespace std; double weightconversion(double); double feettoinches(double); double inchestometers(double); double bmicalc(double); const int feet_inches = 12; const double inches_meters = 0.0254; const double lbs_kilos = 2.2; int weight_lbs = 0; int height_feet = 0; int height_inches = 0; double weight_kilos = 0.0; double height_meters = 0.0; double heightininches = 0; double bmi = 0.0; int main() { cout << "Enter your weight: "; // User input values cin >> weight_lbs; cout << endl << "Enter your height in feet and inches: "; cin >> height_feet >> height_inches; weight_kilos = weightconversion(weight_lbs); heightininches = feettoinches(); height_meters = inchestometers(heightininches); bmi = bmicalc(); cout << endl << "Your BMI is: " << bmi << endl; system("PAUSE"); return 0; } double weightconversion(double) // Function for conversion of weight { weight_kilos = weight_lbs * lbs_kilos; return weight_kilos; } int feettoinches() // Function for conversion of height to inches { heightininches = (height_feet * feet_inches) + height_inches; return heightininches; } double inchestometers(double) // Function for conversion inches to meters { height_meters = heightininches * 0.0254; return height_meters; } double bmicalc() // Function to calculate BMI { bmi = weight_kilos * (height_meters * height_meters); return bmi; } // Programming exercise 3.2 - figuring BMI #include <iostream> using namespace std; double weightconversion(double); double feettoinches(double); double inchestometers(double); double bmicalc(double); const int feet_inches = 12; const double inches_meters = 0.0254; const double lbs_kilos = 2.2; int weight_lbs = 0; int height_feet = 0; int height_inches = 0; double weight_kilos = 0.0; double height_meters = 0.0; double heightininches = 0; double bmi = 0.0; int main() { cout << "Enter your weight: "; // User input values cin >> weight_lbs; cout << endl << "Enter your height in feet and inches: "; cin >> height_feet >> height_inches; weight_kilos = weightconversion(weight_lbs); heightininches = feettoinches(); height_meters = inchestometers(heightininches); bmi = bmicalc(); cout << endl << "Your BMI is: " << bmi << endl; system("PAUSE"); return 0; } double weightconversion(double) // Function for conversion of weight { weight_kilos = weight_lbs * lbs_kilos; return weight_kilos; } int feettoinches() // Function for conversion of height to inches { heightininches = (height_feet * feet_inches) + height_inches; return heightininches; } double inchestometers(double) // Function for conversion inches to meters { height_meters = heightininches * 0.0254; return height_meters; } double bmicalc() // Function to calculate BMI { bmi = weight_kilos * (height_meters * height_meters); return bmi; }

Sep 11th, 2005, 10:44 AM	#7
coldDeath Expert Programmer Join Date: Aug 2005 Location: UK Posts: 862 Rep Power: 4	Too few arguments means that you created a function and when you called it you didnt use the right amount of arguments. example: (Toggle Plain Text) //simple function int multiply (int a, int b) { int sum; sum = a * b; return sum; } //pretend this is where you want to call the function. multiply(2,3); //that would give you the answer 6 //but if you call it like this: multiply(6); //it will say: too few arguments, because you only supplied one and the function needs two. //simple function int multiply (int a, int b) { int sum; sum = a * b; return sum; } //pretend this is where you want to call the function. multiply(2,3); //that would give you the answer 6 //but if you call it like this: multiply(6); //it will say: too few arguments, because you only supplied one and the function needs two. Hope i have helped. __________________ Programming Tutorials - Linux Installation Guide - Learn Python - Learn C++ Got Slack? Join us at #programmingforums @ irc.freenode.net! My software never has bugs. It just develops random features.

Sep 11th, 2005, 10:53 AM	#8
meverha1 Newbie Join Date: Sep 2005 Posts: 11 Rep Power: 0	So I can't do something like this: (Toggle Plain Text) ... double function1(double); ... double function1() { ... } ... double function1(double); ... double function1() { ... } Basically, I delclare a function at the beginning of the program and then use it later with empty brackets, like I could "main()"?

Sep 11th, 2005, 10:59 AM	#9
coldDeath Expert Programmer Join Date: Aug 2005 Location: UK Posts: 862 Rep Power: 4	nono. You make you function first. (Toggle Plain Text) double function1(){ ... } double function1(){ ... } Then in the main() function you call it like this: (Toggle Plain Text) funtion1(); funtion1(); You only write stuff inbetween the ( and ) (when making a function) when you want an argument to the function. __________________ Programming Tutorials - Linux Installation Guide - Learn Python - Learn C++ Got Slack? Join us at #programmingforums @ irc.freenode.net! My software never has bugs. It just develops random features.

Sep 11th, 2005, 11:04 AM	#10
meverha1 Newbie Join Date: Sep 2005 Posts: 11 Rep Power: 0	Ok, I think I corrected it. Basically when I called the functions in "main()" I had to do this: (Toggle Plain Text) weight_kilos = weightconversion(weight_lbs); weight_kilos = weightconversion(weight_lbs); What I was originally trying to do was this: (Toggle Plain Text) weight_kilos = weightconversion(); weight_kilos = weightconversion(); So, when I call a function in main I always have to assign some sort of value to it between "()"?

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Programming Forums > Application Development > C++

Simple Function Questions