I've been working on this homework assignment for a while and am about ready to pull my hair out.
I need help rounding a float to the tenths place while still showing a 0 in the hundredths place and nothing I do seems to do that.
i.e. 2.47 = 2.50
#include "stdafx.h"
#include <iostream>
#include <iomanip>
using namespace std;
int main()
{
float MPH;
float seconds;
const float MPH2MPS = (1609.00 / 3600.00);
float a;
cout << " Acceleration calculator" << endl;
cout << "" << endl;
cout << "Please enter the velocity in miles per hour: ";
cin >> MPH;
cout << "" << endl;
cout << "Please enter the time in secounds: ";
cin >> seconds;
cout << "" << endl;
cout << "" << endl;
cout << "" << endl;
a = MPH2MPS * ( MPH / seconds );
cout << showpoint << fixed << setprecision(2);
cout << "The acceleration required by a vehicle to reach" << endl;
cout << "" << endl;
cout << "a velocity of " << MPH << " miles per hour in " << seconds << " seconds" << endl;
cout << "" << endl;
cout << "is " << setprecision(1) << a << " meters per second" << endl;
cout << "" << endl;
cout << "" << endl;
system("pause");
return 0;
Any ideas?
Reading #asterite's answer here:
cout << "is " << static_cast<double>(std::round(a * 10)) / 10 << " meters per second" << endl;
Note the round function only works if you #include <cmath>
Update:
Modified math.h with cmath, thanks to #user4581301
Related
I am trying to create a C++ program that calculates sales tax for a customer and displays a receipt. For example, if you entered 10 as the first sale amount and the tax rate is 0.0825 it should display the total tax as $0.83. Why does my subtotal and total due at the end of the receipt display $10.82 when it should be $10.83?
//Customer Receipt
#include <iostream>
#include <iomanip>
#include <vector>
using namespace std;
struct Item_Receipt
{
double item;
double cost;
double tax;
double subtotal;
};
int main()
{
vector <Item_Receipt> Store_Receipt;
Item_Receipt Purchase;
//Variables
const double item_tax = .0825;
double Item_Total = 0.0;
double Tax_Total = 0.0;
double Total_Sales = 0.0;
int numSales = 0;
cout << "First sales amount (Enter a 0 to stop): ";
cin >> Purchase.item;
Purchase.tax = Purchase.item * item_tax;
Purchase.subtotal = Purchase.item + Purchase.tax;
Store_Receipt.push_back(Purchase);
Item_Total += Purchase.item;
Tax_Total += Purchase.tax;
Total_Sales += Purchase.subtotal;
numSales++;
while (Purchase.item > 0.0)
{
cout << "Next sales amount (Enter a 0 to stop): ";
cin >> Purchase.item;
if(Purchase.item > 0.0)
{
Purchase.tax = Purchase.item * item_tax;
Purchase.subtotal = Purchase.item + Purchase.tax;
Store_Receipt.push_back(Purchase);
Item_Total += Purchase.item;
Tax_Total += Purchase.tax;
Total_Sales += Purchase.subtotal;
numSales++;
}
else
cout << endl << "That was the last item being puchased.\nHere is your itemized receipt." << endl << endl;
}
//end while
//Output
cout << "----------------------------------------- " << endl;
cout << "\tReceipt of Purchase" << endl;
cout << "----------------------------------------- " << endl << endl;
cout << fixed << setprecision(2);
cout << setw(10) << "Item Cost" <<
setw(15) << "Item Tax" <<
setw(15) << "Subtotal" << '\n';
cout << "----------------------------------------- " << endl;
for(int x=0;x<numSales;x++)
cout << setw(8) << Store_Receipt[x].item << setw(15) << Store_Receipt[x].tax <<
setw(15) << Store_Receipt[x].subtotal << endl;
cout << "----------------------------------------- " << endl;
cout << setw(10) << "Item Total" <<
setw(15) << "Tax Total" <<
setw(15) << "Total Due" << endl;
cout << setw(8) << Item_Total << setw(15) << Tax_Total <<
setw(15) << Total_Sales << endl;
cout << "----------------------------------------- " << endl;
cout << "\tYou purchased " << numSales << " items." << endl;
cout << "----------------------------------------- " << endl;
cout << "\tThank you! Have a nice day!" << endl;
cout << "----------------------------------------- " << endl;
cin >> numSales;
return 0;
}
setprecision(2) doesn't mean "round to 2 decimal digits," it means "display 2 decimal digits." The actual value is 10.825 but you're only displaying the first two decimal digits.
If you want to round away from the midpoint, you need to use one of the rounding functions on the result.
Since you want to round to the second decimal place, you have to first multiply the number by 100, then round it, then divide by 100. You could do this with the help of a function:
double round_to_cents(double v) {
return std::round(v * 100) / 100;
}
Then round the tax calculation:
Purchase.tax = round_to_cents(Purchase.item * item_tax);
(Demo)
I seem to be having a problem with a C++ coding question. It involves mathematical arithmetic and I seem to be getting all of my outputs correct except the final one. In addition to this, the decimal point format of my answers seem to be incorrect. The answers should contain two decimal places but only two out of my four decimal point answers seem to have two decimal places. When I try to use the precision() function, the answers go into scientific notation which I do not want.
Here is the question and answer:
Here is my code:
#include <iostream>
#include <iomanip>
#include <cmath>
using namespace std;
int main()
{
float principal;
float interest_rate;
float times_compounded;
cout << "Hello, please enter a value for your principal: ";
cin >> principal;
cout << principal << endl;
cout << "Please enter a value for your interest rate: ";
cin >> interest_rate;
cout << interest_rate << "%" << endl;
cout << "Please enter the number of times the interest is compounded during the year: ";
cin >> times_compounded;
cout << times_compounded << endl << endl;
float interest = interest_rate * 10.197647;
float amount = principal * pow((1 + (interest_rate/times_compounded)), times_compounded);
cout << "Interest Rate: " << setw(19) << interest_rate << "%" << endl;
cout << "Times Compounded: " << setw(17) << times_compounded << endl;
cout << "Principal: " << setw(17) << "$ " << setw(7) << principal << endl;
cout << "Interest: " << setw(20) << "$ " << interest << endl;
cout << "Amount in Savings: " << setw(9) << "$ " << amount;
return 0;
}
Here are my three inputs:
1000, 4.25, 12
Any feedback would be appreciated, thank you for your time.
First, the last value is wrong because you're using the interest rate as a normal number in the formula although it's actually a percentage. So you'd need to divide it by 100:
float amount = principal * pow((1 + ((interest_rate / 100) /times_compounded)), times_compounded);
Now for the precision, you can use std::fixed in conjunction with std::setprecision to set the default floating point printing precision when using std::cout. We can use a macro to make it more readable, like:
#define FIXED_FLOAT(x, p) std::fixed<<std::setprecision(p)<<(x)
So, the full output section would look like:
cout << "Interest Rate: " << setw(19) << FIXED_FLOAT(interest_rate, 2) << "%" << endl;
cout << "Times Compounded: " << setw(17) << FIXED_FLOAT(times_compounded, 0) << endl;
cout << "Principal: " << setw(17) << "$ " << setw(7) << FIXED_FLOAT(principal, 2) << endl;
cout << "Interest: " << setw(20) << "$ " << FIXED_FLOAT(interest, 2) << endl;
cout << "Amount in Savings: " << setw(9) << "$ " << FIXED_FLOAT(amount, 2);
Also, that interest = interest_rate * 10.197647 seems fishy. Interest should just be the amount minus the principal.
So I'm writing a basic application and for some reason when I run the program a bunch of numbers pop up before my intended output. It was working fine until I added the "std::cout" lines to have the outputs only be 2 decimals. The general gist of the application is a program acts as a self-checkout register at a store and lets the user buy 2 items. And yes I know the code probably looks really bad, I'm still super new to C++.
#include <iostream>
#include <iomanip>
using namespace std;
int main()
{
float price1;
float number1;
float price2;
float number2;
float priceofitemplustax1;
float priceofitemplustax2;
float total;
std::cout << std::fixed;
std::cout << std::setprecision(2);
std::cout << price1;
std::cout << price2;
std::cout << priceofitemplustax1;
std::cout << priceofitemplustax2;
std::cout << total;
cout << endl << "Please scan your first item." <<endl;
cin.get();
cout << endl << "How many of that item are you buying? "<<endl;
cin >> number1;
cout << endl << "How much is that item?"<<endl;
cin >> price1;
priceofitemplustax1 = (number1 * price1) * 1.0875;
cout << endl << "So you want " << number1 << " of this item? Adding tax that will be " << priceofitemplustax1 << "."<<endl;
cin.get();
cout << endl << "Please scan your second item."<<endl;
cin.get();
cout << endl << "How many of that item are you buying? "<<endl;
cin >> number2;
cout << endl << "How much is that item?"<<endl;
cin >> price2;
priceofitemplustax2 = (number2 * price2) * 1.0875;
cout << endl << "So you want " << number2 << " of this item? Adding tax that will be " << priceofitemplustax2 << "."<<endl;
cin.get();
total = priceofitemplustax1 + priceofitemplustax2;
cout << endl << "So your final total for this shopping trip including tax is " << total << "."<<endl;
cin.get();
cout << endl << "Your reciept will print below."<<endl;
cin.get();
cout << setw(14) << right << "Number of Item" << setw(10) << right << "Price" << setw(20) << "Price plus tax" << endl;
cout << setw(14) << right << number1 << setw(10) << right << price1 << setw(20) << priceofitemplustax1 << endl;
cout << setw(14) << right << number2 << setw(10) << right << price2 << setw(20) << priceofitemplustax2 << endl;
cout << endl;
cout << endl;
cout << setw(8) << right << "Total is" << setw(10) << total << price2 << endl;
cin.get();
}
std::cout << std::setprecision(2);
std::cout << price1;
std::cout << price2;
std::cout << priceofitemplustax1;
std::cout << priceofitemplustax2; std::cout << total;
here you write 5 floats
The lines
std::cout << std::fixed; // sets a format
std::cout << std::setprecision(2); // sets a format
set the streams output format.
The lines
std::cout << price1; // outputs a number
std::cout << price2; // outputs a number
std::cout << priceofitemplustax1; // outputs a number
std::cout << priceofitemplustax2; // outputs a number
std::cout << total; // outputs a number
print the variables to the stream.
Just remove the variable output lines. Do not accept this answer - Credit goes to manni66
assignment at school asks me to find the present value using double, and void. i was able to write my code up to a certain degree but the result is not what i was expecting.. i ended up separating the present value into different section so at the end i'd multiply the amount given with the rest.. any tips on how to make the code actually work the way its supposed to?
#include <iostream>
#include <cmath>
using namespace std;
int main()
{
double payment,year_term, interest;
double sum;
double Power;
double presentv;
double present;
cout << "Hello, how are you doing?" << endl;
cout << "Please insert a payment amount" << endl;
cin >> payment;
cout << " amount inserted: " << payment << endl;
cout << "Enter number of years" << endl;
cin >> year_term;
cout << " number of years: " << year_term << endl;
cout << "Enter interest rate" << endl;
cin >> interest;
cout << " the interest is: " << interest << "%" << endl;
Presentv = ((1 - (pow((1 + interest),year_term))))/interest;
cout << " the value: " << Presentv << endl;
presentva = payment * Presentv;
cout << " the present value is: " << presentva << endl;
}
I'm having some issues using setprecision. I don't understand how it works completely. I searched the problem and was able to extrapolate some code that should've worked. I don't understand why it's not. Thank you for your help, I'm still kind of new at this.
//monthly paycheck.cpp
//Paycheck Calculator
#include <iostream>
#include <iomanip>
#include <string>
using namespace std;
int main() {
//Constants
const double
FEDERAL_TAX = 0.15, //Federal Tax
STATE_TAX = 0.035, //State Tax
SSA_TAX = 0.085, //Social Security & Medicare
HEALTH_INSURANCE = 75; //Health Insurance
//Variables
int year;
double grossAmount;
string employeeName, month;
// Initialize variables with input
cout << "Hello, what's your first name? ";
cin >> employeeName;
cout << "What is your gross amount? ";
cin >> grossAmount;
cout << "Please enter the month and year: ";
cin >> month >> year;
// Output
cout << "***********************************" << endl;
cout << "Paycheck" << endl;
cout << "Month: " << month << "\tYear: " << year << endl;
cout << "Employee Name: " << employeeName << endl;
cout << "***********************************" << endl;
cout << setprecision(5) << fixed;
cout << "Gross Amount: $" << grossAmount << endl;
cout << "Federal Tax: $" << FEDERAL_TAX*grossAmount << endl;
cout << "State Tax: $" << STATE_TAX*grossAmount << endl;
cout << "Social Sec / Medicare: $" << SSA_TAX*grossAmount << endl;
cout << "Health Insurance: $" << HEALTH_INSURANCE << endl << endl;
cout << "Net Amount: $" << fixed << grossAmount-grossAmount*(FEDERAL_TAX+STATE_TAX+SSA_TAX)-HEALTH_INSURANCE << endl << endl;
system("PAUSE");
return 0;
}
If you want to format floats to display with 2 decimal places in C++ streams, you could easily:
float a = 5.1258f;
std::cout << std::fixed << std::setprecision(2) << a << std::endl;
See std::fixed and std::setprecision
Use stream manipulators:
std::cout.fixed;
std::cout.precision(Number_of_digits_after_the_decimal_point);