This question already has answers here:
Why did I get the compile error "Use of unassigned local variable"?
(10 answers)
Closed 4 days ago.
I keep getting this error for annualRate, monthlyCharge, and lateFee.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace Lab_5___Danny_Curro
{
class Program
{
static void Main(string[] args)
{
string firstName;
string lastName;
int accNumber;
string creditPlan;
double balance;
string status;
Boolean late = false;
double lateFee;
double monthlyCharge;
double annualRate;
double netBalance;
Console.Write("Enter First Name: ");
firstName = Console.ReadLine();
Console.Write("Enter Last Name: ");
lastName = Console.ReadLine();
Console.Write("Enter Account Number: ");
accNumber = Convert.ToInt32(Console.ReadLine());
Console.Write("Enter Credit Card Plan Number[Blank Will Enter Plan 0]: ");
creditPlan = Console.ReadLine();
Console.Write("Enter Balance: ");
balance = Convert.ToDouble(Console.ReadLine());
Console.Write("Is This Account Late?: ");
status = Console.ReadLine().Trim().ToLower();
if (creditPlan == "0")
{
annualRate = 0.35; //35%
lateFee = 0.0;
monthlyCharge = balance * (annualRate * (1 / 12));
return;
}
if (creditPlan == "1")
{
annualRate = 0.30; //30%
if (status == "y")
{
late = true;
}
else if (status == "n")
{
late = false;
}
if (late == true)
{
lateFee = 25.00;
}
monthlyCharge = balance * (annualRate * (1 / 12));
return;
}
if (creditPlan == "2")
{
annualRate = 0.20; //20%
if (status == "y")
{
late = true;
}
else if (status == "n")
{
late = false;
}
if (late == true)
{
lateFee = 35.00;
}
if (balance > 100)
{
monthlyCharge = balance * (annualRate * (1 / 12));
}
else
{
monthlyCharge = 0;
}
return;
}
if (creditPlan == "3")
{
annualRate = 0.15; //15%
lateFee = 0.00;
if (balance > 500)
{
monthlyCharge = (balance - 500) * (annualRate * (1 / 12));
}
else
{
monthlyCharge = 0;
}
return;
}
netBalance = balance - (lateFee + monthlyCharge);
Console.WriteLine("Name: \t\t\t {0} {1}", firstName, lastName);
Console.WriteLine("Account Number: \t{0}", accNumber);
Console.WriteLine("Credit Plane: \t\t{0}",creditPlan);
Console.WriteLine("Account Late: \t\t{0}", late);
Console.WriteLine("Balance: \t\t{0}", balance);
Console.WriteLine("Late Fee: \t\t{0}", lateFee);
Console.WriteLine("Interest Charge: \t{0}", monthlyCharge);
Console.WriteLine("Net Balance: \t\t{0}",netBalance);
Console.WriteLine("Annual Rate: \t\t{0}", annualRate);
Console.ReadKey();
}
}
}
The compiler isn't smart enough to know that at least one of your if blocks will be executed. Therefore, it doesn't see that variables like annualRate will be assigned no matter what. Here's how you can make the compiler understand:
if (creditPlan == "0")
{
// ...
}
else if (creditPlan == "1")
{
// ...
}
else if (creditPlan == "2")
{
// ...
}
else
{
// ...
}
The compiler knows that with an if/else block, one of the blocks is guaranteed to be executed, and therefore if you're assigning the variable in all of the blocks, it won't give the compiler error.
By the way, you can also use a switch statement instead of ifs to maybe make your code cleaner.
Change your declarations to this:
double lateFee = 0.0;
double monthlyCharge = 0.0;
double annualRate = 0.0;
The error is caused because there is at least one path through your code where these variables end up not getting set to anything.
Because if none of the if statements evaluate to true then the local variable will be unassigned. Throw an else statement in there and assign some values to those variables in case the if statements don't evaluate to true. Post back here if that doesn't make the error go away.
Your other option is to initialize the variables to some default value when you declare them at the beginning of your code.
Give them a default value:
double lateFee=0.0;
double monthlyCharge = 0.0;
double annualRate = 0.0;
Basically, all possible paths don't initialize these variables.
Use the keyword "default"!!!
string myString = default;
double myDouble = default;
if(!String.IsNullOrEmpty(myString))
myDouble = 1.5;
return myDouble;
There are many paths through your code whereby your variables are not initialized, which is why the compiler complains.
Specifically, you are not validating the user input for creditPlan - if the user enters a value of anything else than "0","1","2" or "3", then none of the branches indicated will be executed (and creditPlan will not be defaulted to zero as per your user prompt).
As others have mentioned, the compiler error can be avoided by either a default initialization of all derived variables before the branches are checked, OR ensuring that at least one of the branches is executed (viz, mutual exclusivity of the branches, with a fall through else statement).
I would however like to point out other potential improvements:
Validate user input before you trust it for use in your code.
Model the parameters as a whole - there are several properties and calculations applicable to each plan.
Use more appropriate types for data. e.g. CreditPlan appears to have a finite domain and is better suited to an enumeration or Dictionary than a string. Financial data and percentages should always be modelled as decimal, not double to avoid rounding issues, and 'status' appears to be a boolean.
DRY up repetitive code. The calculation, monthlyCharge = balance * annualRate * (1/12)) is common to more than one branch. For maintenance reasons, do not duplicate this code.
Possibly more advanced, but note that Functions are now first class citizens of C#, so you can assign a function or lambda as a property, field or parameter!.
e.g. here is an alternative representation of your model:
// Keep all Credit Plan parameters together in a model
public class CreditPlan
{
public Func<decimal, decimal, decimal> MonthlyCharge { get; set; }
public decimal AnnualRate { get; set; }
public Func<bool, Decimal> LateFee { get; set; }
}
// DRY up repeated calculations
static private decimal StandardMonthlyCharge(decimal balance, decimal annualRate)
{
return balance * annualRate / 12;
}
public static Dictionary<int, CreditPlan> CreditPlans = new Dictionary<int, CreditPlan>
{
{ 0, new CreditPlan
{
AnnualRate = .35M,
LateFee = _ => 0.0M,
MonthlyCharge = StandardMonthlyCharge
}
},
{ 1, new CreditPlan
{
AnnualRate = .30M,
LateFee = late => late ? 0 : 25.0M,
MonthlyCharge = StandardMonthlyCharge
}
},
{ 2, new CreditPlan
{
AnnualRate = .20M,
LateFee = late => late ? 0 : 35.0M,
MonthlyCharge = (balance, annualRate) => balance > 100
? balance * annualRate / 12
: 0
}
},
{ 3, new CreditPlan
{
AnnualRate = .15M,
LateFee = _ => 0.0M,
MonthlyCharge = (balance, annualRate) => balance > 500
? (balance - 500) * annualRate / 12
: 0
}
}
};
Your assignments are all nested within your conditional if blocks which means that there is potential for them to never be assigned.
At the top of your class, initialise them to 0 or some other value
The compiler is saying that annualRate will not have a value if the CreditPlan is not recognised.
When creating the local variables ( annualRate, monthlyCharge, and lateFee) assign a default value (0) to them.
Also, you should display an error if the credit plan is unknown.
Not all code paths set a value for lateFee. You may want to set a default value for it at the top.
You don't assign values outside of the if statements ... and it is possible that credit might be something other than 0, 1, 2, or 3, as #iomaxx noted.
Try changing the separate if statements to a single if/else if/else if/else. Or assign default values up at the top.
If you declare the variable "annualRate" like
class Program
{
**static double annualRate;**
public static void Main() {
Try it..
Related
Can someone help me modify my work? Help me add:
An error message when the user tries to enter decimal values.
A third operand for the calculator.
An error message when the user tries to enter any string value other than “exit”.
Here's my code:
class Program
{
static void Main(string[] args)
{
do
{
Console.Write("x = ");
string str = Console.ReadLine();
if (str == "exit")
{
Console.WriteLine("The Programme has stopped");
continue;
}
else
{
int x = Convert.ToInt32(str);
Console.Write("y = ");
int y = Convert.ToInt32(Console.ReadLine());
int sum = x / y;
Console.WriteLine("Result: {0}", sum);
}
}
while (true);
}
}
I'd be very grateful.
Here is a function you can use:
public static bool HasDecimals(decimal x) {
return Decimal.Round(x, 0) != x;
}
If I were going to do this, I'd create a function that I can use to handle most of the user interaction (emitting the prompt, parsing the input string, deciding if "Exit" was entered). In the code below, I kinda-sorta use the standard TryGetXxx pattern.
In this code below, if the TryGetDecimalValueWithPrompt returns true, then a properly parsed number is returned in the output. If it returns false, then the user has chosen to quit.
So, I start with that function:
public static bool TryGetDecimalValueWithPrompt(string prompt, out decimal outputValue)
{
while (true)
{
Console.Write(prompt + " > ");
var response = Console.ReadLine();
if (response.Equals("exit", StringComparison.OrdinalIgnoreCase) || response.Equals("quit", StringComparison.OrdinalIgnoreCase))
{
outputValue = 0.0m;
return false;
}
if (decimal.TryParse(response, out outputValue))
{
return true;
}
//otherwise, failure, so try again
Console.WriteLine("Sorry, incorrect format, try entering a correctly formatted decimal again");
}
}
The while(true) statement says Loop Forever. In this case, Forever lasts until the user has entered a properly formatted number or one of the "exit" keywords.
Then I construct my program around it:
if (!TryGetDecimalValueWithPrompt("Enter the first operand", out var operand1))
{
return;
}
if (!TryGetDecimalValueWithPrompt("Enter the second operand", out var operand2))
{
return;
}
if (operand2 == 0.0m)
{
Console.WriteLine("Sorry, you can't divide by zero");
return;
}
Console.WriteLine($"The result of op1/op2 is {operand1 / operand2}");
If you don't want to allow decimals being entered, change the TryGetDecimalValueWithPrompt function to work with integers instead:
public static bool TryGetIntValueWithPrompt(string prompt, out int outputValue)
{
while (true)
{
Console.Write(prompt + " > ");
var response = Console.ReadLine();
if (response.Equals("exit", StringComparison.OrdinalIgnoreCase) || response.Equals("quit", StringComparison.OrdinalIgnoreCase))
{
outputValue = 0;
return false;
}
if (int.TryParse(response, out outputValue))
{
return true;
}
//otherwise, failure, so try again
Console.WriteLine("Sorry, incorrect format, try entering a correctly formatted integer again");
}
}
If you work with integers, remember that integer division always yields an integer. For example, if you use integers in 7 / 2, the result will be 3, not 3.5. If you want 3.5, do something like 7 / (decimal) 2 (at that point, you are dividing an integer by a decimal and you'll get a decimal).
By the way, if you wanted to prompt for the operator (+, -, *, or /), you could create a TryGetOperator function in the same pattern and just check whatever you get from the user with something like:
var operators = new[] { "+", "-", "*", "/" };
bool goodOperator = operators.Contains(inputFromUser);
I want to make a calculator that asks what you want to do, e.g. add, subtract, etc. It should then use if-statements to perform the different kinds of calculations.
But now when I have gotten to division, I'm wondering how to handle division by 0. I want the program to warn the user when he/she enters a 0, saying something like "sorry you can't divide by 0".
I still want it to calculate the result if the denominator isn't 0.
The error i get is that i can't write:
if (Num02 == "0") because I can't use ints or doubles etc.
How do I fix this in a nice way to show my class/teacher next week?
Here's my code:
using System;
namespace Calculator
{
class MainClass
{
static void Main(string[] args)
{
Start:
int Num01;
int Num02;
string Answer;
Console.WriteLine("What do you want to do?");
Answer = Console.ReadLine();
if (Answer == "Division")
{
Console.WriteLine("Write number");
Num01 = Convert.ToInt32(Console.ReadLine());
Console.WriteLine("Divided by?");
Num02 = Convert.ToInt32(Console.ReadLine());
Console.WriteLine(Num01 + "/" + Num02 + "=" +
(Num01 / Num02));
}
}
}
}
the error i seem to get is that i cant write:
"if (num02 == "0")" because i cant use ints or doubles etc.
You were most certainly on the right track. By adding quotes around the "0", you were comparing a variable of type int (Num02) with a string. Instead, use a literal 0 (without quotes):
if (Num02 == 0)
{
// print warning here
}
else
{
// do division and print result
}
I suggest extracting method for the user input (where we can check syntax - what if user put bla-bla-bla instead of number, extra condition(s) - we don't accept 0 as a second number etc.):
private static int ReadValue(string title,
Func<int, bool> extraCondition = null,
string extraConditionText = null) {
int result;
while (true) { // keep on asking until correct input provided
Console.WriteLine(title);
if (!int.TryParse(Console.ReadLine(), out result)) // syntax check
Console.WriteLine("Syntax error, please, input integer value");
else if (extraCondition != null && !extraCondition(result)) // extra check if any
Console.WriteLine(string.IsNullOrEmpty(extraConditionText)
? "Incorrect value"
: extraConditionText);
else
return result;
}
}
Then you can put
static void Main(string[] args) {
while (true) {
int Num01;
int Num02;
Console.WriteLine("What do you want to do?");
string Answer = Console.ReadLine().Trim();
if (string.Equals(Answer, "Quit", StringComparison.OrdinalIgnoreCase)) {
break;
}
else if (string.Equals(Answer, "Division", StringComparison.OrdinalIgnoreCase)) {
Num1 = ReadValue("Write number");
Num2 = ReadValue("Divided by?", x => x != 0, "Sorry you can't divide by 0");
Console.WriteLine($"{Num1} / {Num2} = {Num1 / Num2}");
}
else {
Console.WriteLine("Sorry, it's an incorrect option");
}
}
}
I'm new to the concept of methods in C#, and I am trying to wrap my head around solving this problem that uses methods to calculate compound interest. I am having a couple problems with the code itself, but the main concept I am struggling with is how to return the variable "double finalAmount" through the use of my methods CalculateCompoundInterest (both variations). Here is my code so far:
using System;
namespace CompoundInterestCalculator
{
public class CompoundCalculator
{
const int EXIT = 0;
const int CALCULATE_DAILY = 1;
const int CALCULATE_QUARTERLY = 2;
const int CALCULATE_VARIABLE = 3;
const int NUM_OPTIONS = 3;
public static void Main()
{
int menuOption;
WelcomeMessage();
do
{
DisplayMenu();
menuOption = ReadOption();
if (menuOption != EXIT)
{
double finalAmount = CalculateInterest(menuOption);
OutputResult(finalAmount);
}
} while (menuOption != EXIT);
ExitProgram();
} // end Main
// Fill in the appropriate modifier and return type (_ _) in the method declaration
public static void WelcomeMessage()
{
Console.WriteLine("\n\n\tCompound Interest Calculator\n");
} // end WelcomeMessage
// Fill in the appropriate modifier and return type (_ _) in the method declaration
public static void ExitProgram()
{
Console.Write("\n\nPress enter to exit.");
Console.ReadLine();
} // end ExitProgram
static void DisplayMenu()
{
string menu = "\n\n1) Calculate final amount after interest (compounded daily)"
+ "\n2) Calculate final amount after interest (compounded quarterly)"
+ "\n3) Calculate final amount after interest (define number of times compounded yearly)"
+ "\n\nEnter your option(1-3 or 0 to exit): ";
Console.Write(menu);
} // end DisplayMenu
public static void OutputResult(double finalAmount)
{
// Display the message "The final amount of money plus interest is: $(amount)"
// The amount should display as currency, with two decimal places, e.g. $10,000.00
Console.WriteLine("The final amount of money plus interest is: ${0.2}", finalAmount);
} // end OutputResult
static int ReadOption()
{
string choice;
int option;
bool okayChoice;
do
{
choice = Console.ReadLine();
okayChoice = int.TryParse(choice, out option);
if (!okayChoice || option < 0 || option > NUM_OPTIONS)
{
okayChoice = false;
Console.WriteLine("You did not enter a correct option.\n\n Please try again");
DisplayMenu();
}
} while (!okayChoice);
return option;
} // end ReadOption
public static double CalculateInterest(int menuOption)
{
// (For this exercise, we will assume the user is inputting correct input.)
double principal;
double interestRate;
int numYears;
double finalAmount;
Console.Write("Enter the principal amount: ");
principal = Double.Parse(Console.ReadLine());
Console.Write("Enter the interest rate: ");
interestRate = Double.Parse(Console.ReadLine());
Console.Write("Enter the number of years that interest is accumulated for: ");
numYears = Int32.Parse(Console.ReadLine());
if (menuOption == CALCULATE_DAILY || menuOption == CALCULATE_QUARTERLY)
{
if (menuOption == CALCULATE_DAILY)
{
// Call the appropriate CalculateCompoundInterest method
CalculateCompoundInterest( principal, interestRate, numYears);
}
else
{
// Call the appropriate CalculateCompoundInterest method
CalculateCompoundInterest( principal, interestRate, numYears, 4);
}
}
else
{
Console.Write("Enter the number of times the interest is compounded yearly: ");
int numTimesCompounded = Int32.Parse(Console.ReadLine());
// Call the appropriate CalculateCompoundInterest method
CalculateCompoundInterest( principal, interestRate, numYears, numTimesCompounded);
}
Console.WriteLine();
// return the amount calculated by the compound interest method
return finalAmount;
} // End CalculateInterest
// Declare and implement the method CalculateCompoundInterest whose parameters are the principal, interest rate, and number of years (in that order)- make sure it is public!
// For the declaration select an appropriate modifier, return type, and types for the parameters
// This version assumes the interest is compounded daily (365 times a year)
// For both methods, you should assume the interest rate is input already in decimal form (i.e. 0.02 rather than 2 for a 2% rate)
public static double CalculateCompoundInterest(double principal, double interestRate, int numYears )
{
double compoundInterest;
compoundInterest = principal * Math.Pow(1 + interestRate / numYears, 1);
return compoundInterest;
}
// Declare and implement the method CalculateCompoundInterest whose parameters are the principal, interest rate, number of years, and number of times compounded yearly - make sure it is public!
// For the declaration select an appropriate modifier, return type, and types for the parameters
// This version allows the number of times compounded yearly to be specified.
public static double CalculateCompoundInterest(double principal, double interestRate, int numYears, int numTimesCompounded)
{
double compoundInterest;
compoundInterest = principal * Math.Pow(1 + interestRate / numYears, numTimesCompounded);
return compoundInterest;
}
}//end class
}//end namespace
Basically I am trying to figure out how to obtain results from methods, and how to use them in other methods (e.g. for value/parameter arithmetic). Feel free to let me know if you think there is something else that is wrong with the purpose of the program (to calculate compound interest). Also let me know if this is inappropriate for Stack Overflow, I am new to the website. Thanks guys.
I 'think' this is what you are looking for
var interest = CalculateCompoundInterest( principal, interestRate, numYears, 4);
edit
Additionally you may want to refactor the following 2 methods into 1 method. Hint - optional parameters
public static double CalculateCompoundInterest(double principal, double interestRate, int numYears )
{
double compoundInterest;
compoundInterest = principal * Math.Pow(1 + interestRate / numYears, 1);
return compoundInterest;
}
public static double CalculateCompoundInterest(double principal, double interestRate, int numYears, int numTimesCompounded)
{
double compoundInterest;
compoundInterest = principal * Math.Pow(1 + interestRate / numYears, numTimesCompounded);
return compoundInterest;
}
}
I am a first-timer learning C# and I just started writing my first program. I am currently running into a snag in one of my while loops. Normally I find that outside the loop my variables work like they should, but for some reason Visual Studio is giving me a warning saying that "The variable 'itemPrice' is assigned but its value is never used."
How I can I get that warning to go away and avoid any kind of bad practices?
using System;
class Program
{
public static void Main()
{
// "whoa" <-- string literal
// 43 <-- int literal
// 43.34 <-- double literal
// false <-- bool literal
// 43.4f <-- float literal
// 43f <-- float literal
// 43m <-- decimal literal
bool hasEnteredMoney = false;
decimal money = 0;
int menuSelection;
decimal itemPrice;
bool isValidItem;
string itemName;
while (!hasEnteredMoney)
{
Console.Write("Please enter how much money you have: ");
hasEnteredMoney = decimal.TryParse(Console.ReadLine(), out money);
if (!hasEnteredMoney)
{
Console.WriteLine("Please enter a valid decimal value.");
}
}
while (money >= 3)
{
Console.WriteLine("You have $" + money + " left.");
Console.WriteLine("Please enter your selection:");
Console.WriteLine("[0] - Poke Ball - $200");
Console.WriteLine("[1] - Great Ball - $700");
Console.WriteLine("[2] - Ultra Ball - $1200");
Console.WriteLine("[3] - Potion - $300");
Console.WriteLine("[4] - Antidote - $100");
Console.WriteLine("[5] - Clear Mail - $50");
Console.WriteLine(": ");
if (int.TryParse(Console.ReadLine(), out menuSelection))
{
isValidItem = false;
if (menuSelection == 0)
{
itemPrice = 200;
itemName = "Poke Ball";
isValidItem = true;
}
if (menuSelection == 1)
{
itemPrice = 700;
itemName = "Great Ball";
isValidItem = true;
}
if (menuSelection == 2)
{
itemPrice = 1200;
itemName = "Ultra Ball";
isValidItem = true;
}
if (menuSelection == 3)
{
itemPrice = 300;
itemName = "Potion";
isValidItem = true;
}
if (menuSelection == 4)
{
itemPrice = 100;
itemName = "Antidote";
isValidItem = true;
}
if (menuSelection == 5)
{
itemPrice = 50;
itemName = "Clear Mail";
isValidItem = true;
}
}
else
{
Console.WriteLine("Invalid input.");
}
}
Console.WriteLine("... you ran out of money :(");
Console.ReadKey();
}
}
The variables itemPrice, isValidItem, itemName are being set (being assigned to), but the variables are not being used for other purposes later in the program.
The compiler is warning you that although you are setting itemPrice, isValidItem, and itemName, setting these variables is not doing anything in the program - E.G. when the program is executed, the variables will not have any effect on the operation of the program.
It is giving you this error because your variables are never use in the code.
itemPrice = 200;
itemName = "Poke Ball";
isValidItem = true;
So visual studio intellisense is basicly saying : you putting all those values in your variables, but are never using any of them no where.
If you Console.WriteLine(itemName); at the end of you code, the warning should go away for all the itemName in you loop.
tl;dr You set; them but never get; them
The warning is a good indication that you should actually do something with the value. In your case, I think you would want to do something like
money -= itemPrice;
First, it will get rid of the warning.
Second, it will keep the while loop from running indefinitely :)
Console.Write("Input price: ");
double price;
string inputPrice = Console.ReadLine();
if (double.TryParse(inputPrice, out price))
{
price = double.Parse(inputPrice);
}
else
{
Console.WriteLine("Inventory code is invalid!");
}
so i have to make sure that the price that will be inputed has and must be 2 decimal places. Such as the following:
2.00 - correct
3.65 - correct
77.54 - correct
34.12 - correct
but
2 - wrong
2.8 - wrong
2.415 - wrong
99.0 - wrong
how should i check for it it?
Try this:-
Console.Write("Input price: ");
double price;
string inputPrice = Console.ReadLine();
var num = Decimal.Parse(inputPrice); //Use tryParse here for safety
if (decimal.Round(num , 2) == num)
{
//You pass condition
}
else
{
Console.WriteLine("Inventory code is invalid!");
}
Update
Regex Check:-
var regex = new Regex(#"^\d+\.\d{2}?$"); // ^\d+(\.|\,)\d{2}?$ use this incase your dec separator can be comma or decimal.
var flg = regex.IsMatch(inputPrice);
if(flg)
{
\\its a pass
}
else
{
\\failed
}
check inputPrice.Split('.')[1].Length == 2
UPDATE:
Console.Write("Input price: ");
double price;
string inputPrice = Console.ReadLine();
if (double.TryParse(inputPrice, out price) && inputPrice.Split('.').Length == 2 && inputPrice.Split('.')[1].Length == 2)
{
price = double.Parse(inputPrice);
}
else
{
Console.WriteLine("Inventory code is invalid!");
}