Random Bill Function

[kra9853]

The function Generate_And_Display_Bill() has no formal parameters and returns a variable of type float. The function generates a random number between $0.01 and $99.99 and returns the value to main().

This is what I've created so far in my function declaration;

#include <iostream>
#include <ctime>


float Generate_And_Display_Bill()
{

	float Random_Bill;

	srand(time(NULL));

	for(float index=0.01; index < 99.99; index++)
	{
		Random_Bill = (rand()%99.99)+1;
		cout << Random_Bill << endl; 
	}

	return (Random_Bill);
}

I'm receiving an error telling me that in line 14 the 99.99 must be have integral or enum type, I want to display a random bill with decimals and I've declared Random_Bill as a float, what am I doing wrong?

Also for some odd reason "cout" and "endl" are giving me unidentified error messages even though I have included the iostream library, please help

[Momerath]

for loops require integers as the increment value. Why are you trying to loop through all the valid values? The requirements are to generate one (1) number and return it.

[Nick Evan]

>> Also for some odd reason "cout" and "endl" are giving me unidentified error messages even though I have included the iostream library, please help

did you forget using namespace std; ?

[kra9853]

Thanks @Momerath yeah I don't know why I was trying to create several random numbers I've fixed it so it creates only one random number
And @Nick Evan yes I completely forgot using namespace rookie mistake cout and endl are now recognizable

Here is my revision still getting errors with 99.99 though;

#include <iostream>
#include <ctime>
 
using namespace std;

float Generate_And_Display_Bill()
{

	float Random_Bill;

	srand(time(NULL));

	Random_Bill=(float)((rand()%99.99)*0.01);

	cout << Random_Bill; //Test to see value

	return (Random_Bill);
}

[L7Sqr]

The modulus operator is an integer operation. It returns to you the remainder after integer division. Dividing by a floating point number gives you an exact floating point value (no remainder) so the operation makes no sense. If you want a random floating point value in a particular range I'd suggest you look into the drand48 function as a replacement to the rand call in your code.

[kra9853]

How does drand48() work? is drand48() within the ctime library? If I use it will I have to change line 11 in my code as well?

*I've checked my textbook and I can't find anything on that function

[Nick Evan]

Or you could pick a random number between 0-1000 and divide it by 1000?

[kra9853]

Okay instead of making this more complicated than it needs to be I decided to use rand())/RAND_MAX*100 to produce a float between 0 and 99

float Generate_And_Display_Bill()
{

	float Random_Bill;
	Random_Bill = 0;

	srand((unsigned)time(NULL));


	Random_Bill= (float(rand())/RAND_MAX*100);

	cout << Random_Bill; //Test to see value

	return (Random_Bill);
}

However, my ouput isn't really random at all and I want the output to the hundredths decimal space .00

[L7Sqr]

Seed your random number generator (srand - or one of it's variants). And drand48 is not complicated and does a better job of what you want (no converting and/or modulus).

#include <iostream>
#include <cstdlib>

double use_drand () { return drand48 () * 100.0; }

int main () {
   for (int i = 0; i < 10; ++i)
      std::cout << use_drand () << std::endl;
   return 0;
}

[edit]
You'll want to seed drand48 with srand48.

[L7Sqr]

Seed your random number generator (srand - or one of it's variants). And drand48 is not complicated and does a better job of what you want (no converting and/or modulus).

#include <iostream>
#include <cstdlib>

double use_drand () { return drand48 () * 100.0; }

int main () {
   for (int i = 0; i < 10; ++i)
      std::cout << use_drand () << std::endl;
   return 0;
}

[kra9853]

Because I haven't learned about drand () in my programming class and also because I honestly don't understand how it works either, I stuck with the ol' rand () function and I messed around for a bit until I created pretty random bill generator;

float Generate_And_Display_Bill()
{

	float Random_Bill;
	Random_Bill = 0;

	srand((unsigned)time(NULL));

	while(!(Random_Bill >= .01 && Random_Bill <= 99.99))
	{
		Random_Bill = ((float)rand ())/100;
	}

	cout << Random_Bill; //Test to see value

	return (Random_Bill);
}

so far all my values come out to the hundredths decimal space and stay within the bill range