I am trying to compare two strings for a trivia program, one entered by a user and the other accessed from a node. The comparison is within an IF statement and always returns false. Below is the code used for this function. Both variables userAnswer and answer are of the type string.
cout << "Question: " << cur_ptr->question << endl;
cout << "Answer: ";
getline(cin, userAnswer);
if (userAnswer == cur_ptr->answer) {
cout << "Your answer is correct. You receive " << cur_ptr->points << " points." << endl;
totalPoints += cur_ptr->points;
}
else {
cout << "Your answer is wrong. The correct answer is: " << cur_ptr->answer << endl;
}
cout << "Your total points: " << totalPoints << endl << endl;
cur_ptr = cur_ptr->next;
Whenever my program runs, it generates an output like so
Question: How long was the shortest war on Record? (Hint: how many minutes)?
Answer: 38
Your answer is wrong. The correct answer is: 38
Your total points: 0
getline(cin, userAnswer) is keeping the \n. You might consider trimming the string with something like the following
getline(cin, userAnswer);
userAnswer.erase(userAnswer.find_last_not_of("\n\r") + 1);
No guarantees that this is the answer, but I've run across this a few times and it's just been a trailing \n or \r.
Do some boost::trim() on the strings to compare, before the comparison, and see if that helps.
Related
I am working on a very basic program for my Fundamentals I class and I have everything 98% working as intended.
This program takes the names of three grades, averages them, and outputs them into a table, but since assignmentName[] is on the same line of code as grade[], it pushes grade[] to the right determining on how many characters the user inputted.
Screenshot of the problem
Here is the code I currently have written for the table:
cout << "___________________________\n";
cout << name << "'s Grade Chart\n";
cout << "---------------------------\n";
cout << setprecision(1) << fixed;
cout << "Grade for " << assignmentName[0] << setw(8) << grade[0] << endl;
cout << "Grade for " << assignmentName[1] << setw(8) << grade[1] << endl;
cout << "Grade for " << assignmentName[2] << setw(8) << grade[2] << endl;
cout << "\nYour average grade between those three assignments is: " << setw(1) << avg << endl;`
I commented, "Place another setw(N) where N is a bit bigger than the largest assignmentName before each << assignmentName."
But on second thought it's bit more fun than that, so I figure a real answer is in order.
First, some reading materials:
Documentation on std::left and std::right
Documentation on std::max
And now on with the show!
First we need to know how big the largest assignment name is.
size_t max = 0;
for (const string & assn: assignmentName)
{
max = std::max(max, assn.length());
// You may need
//max = std::max(max, strlen(assn));
// if you've been forced to resort to barbarism and c-style strings
}
max++; // one extra character just in case we get a really long grade.
Sometimes this can get a lot neater. For example std::max_element can eliminate the need for the loop we used to get the maximum assignment name length. In this case we're looking for the size of the string, not the lexical order of the string, so I think the loop and std::max is a bit easier on the brain.
And now to format, we print the names left-justified and the grades right justified, with the names padded max characters and the grades 8 characters.
cout << "Grade for " << std::left << setw(max) << assignmentName[0]
<< std::right << setw(8) << grade[0] << '\n'
<< "Grade for " << std::left << setw(max) << assignmentName[1]
<< std::right << setw(8) << grade[1] << '\n'
<< "Grade for " << std::left << setw(max) << assignmentName[2]
<< std::right << setw(8) << grade[2] << '\n';
Note it's now one big cout. This was done mostly for demonstration purposes and because I think it looks better. It doesn't really save you much, if anything, in processing time. What does save time is the lack of endls. endl is actually a very expensive operation because not only does it end a line, but it also flushes. It forces whatever has been buffered in the stream out to the underlying media, the console in this case. Computers are at their best when they can avoid actually going out of the computer until they really have to. Drawing to the screen is way more expensive than writing to RAM or a cache, so don't do it until you have to.
Instead of writing:
"Grade for " << assignmentName[x] << setw[y] << grade(z)
Write:
"Grade for " << setw[a] << assignmentName[x] << setw[y] << grade(z)
Where a is greater than x in each case.
Maybe that should fix it.
Your a should be something like 10 or 15 or something. I hope it works after that. Try it.
I have a task to make a program that will calculate two numbers put into it.
And also show the calculation between every number.
And if I input a letter not a number the program crashes, this is an more advanced task that I dont need to do but I really want to know how to do this. So that is my question, how do I make the program give me a warning that not to use letters and still give u ability to input numbers if you enter a letter, instead of crashing.
This is how my code looks so far
Blockquote
float nmr1, nmr2;
cout << "Write two numbers.\n";
cin >> nmr1;
cin >> nmr2;
cout << "\n";
cout << nmr1 << " + " << nmr2 << " = " << nmr1 + nmr2 << endl;
cout << nmr1 << " - " << nmr2 << " = " << nmr1 - nmr2 << endl;
cout << nmr1 << " * " << nmr2 << " = " << nmr1 * nmr2 << endl;
cout << nmr1 << " / " << nmr2 << " = " << nmr1 / nmr2 << endl;
cin.get();
cin.get();
return 0;
maybe there are easier things to write but I'm a beginner, and I would use the search tool but I don't know what to search.
cin >> var_of_type_float will return false if the input fails. So simply use that in a conditional expression, something like:
if (cin >> nmr1) { // all ok
If you want to check the input, usual way is to read a string, check if there are non valid character, then parse it into a number (tedious task in C++ with real numbers) and store in a float, finally, perform operations with those floats.
If you are not working with text input yet, I recommend you to wait to implement this feature, as it could be complex for a beginner in programming
To check if a bad input was received via cin you use the following condition:
if(!cin){
// bad input was received, don't use cin again.
}
What really crashes is the divide-by-zero operation.
If invalid number is entered, nmr1 and nmr2 will be 0
and nmr1/nmr2 will crash. You must check for (nmr2 != 0) before attempting to divide.
I've been having trouble doing this assignment. I'm just having a hard time understanding and I am not entirely sure what to do. I've researched and watched videos and havent been able to find the right, specific information. Its a bunch of questions, so I hope someone can not only giveme the answers, but also explain to me so I have a strong understanding :) . Here are the questions:
1)In this exercise we have been given some program code that will accept two integers as inputs
and evaluate which one holds the larger value. This evaluation occurs in multiple places
throughout the code. Write a function that the program could use to perform this same evaluation
instead of duplicating the code over and over. Start by writing a suitable function declaration
towards the beginning of the code file. You will have to decide whether your function will return
some output or not.
2) With your declaration written proceed to define the function, including the appropriate pieces of
code that will evaluate which of the two integers is the largest. If you stated earlier that your
function will return a value, be sure to define what it will return here.
3) Use your result from parts (1) and (2) to reduce the amount of duplicate code in the main function
provided by replacing the multiple instances of the integer comparison with a call to invoke the
function you have created. Remember that the function will require two integers to be passed in
as arguments and if you are returning some value from the function it should be used (stored in
a variable, outputted to screen, etc.). As a word of advice, test your function works correctly after
replacing just one of the evaluations, don’t replace them all at once (if the function works correctly
for the first replacement then it should work for the others).
4) Since the function you have created only compares the values of its parameters and doesn’t write
to them (i.e. change the value stored in them) we should specify in the function declaration and
definition that these parameters should be treated like constants. Make the necessary
modifications to the function and test again to verify the function still works. Confirm the function
will not let you change the data of the parameters by trying to include an operation in the function
that would change the value of one of the variables (e.g. number2 += 10;)
-- Here is the code ( I apologise for the long writing):
#include <iostream>
int main(void)
{
using std::cout;
using std::cin;
using std::endl;
int nNum1 = 10, nNum2 = 11;
cout << "This program will compare two numbers and report which one is larger.\n\n"
<< "Proceeding with evaluation...\n" << endl;
cout << "\nUsing numbers: " << nNum1 << " and " << nNum2 << ", the larger one is: ";
if (nNum1 > nNum2)
cout << nNum1 << endl;
else if (nNum1 < nNum2)
cout << nNum2 << endl;
else
cout << "Neither of them! It's a draw." << endl;
int numberA = 234;
int numberB = 234;
cout << "\nUsing numbers: " << numberA << " and " << numberB << ", the larger one is: ";
if (numberA > numberB)
cout << numberA << endl;
else if (numberA < numberB)
cout << numberB << endl;
else
cout << "Neither of them! It's a draw." << endl;
int one = 'a';
int two = 'A';
cout << "\nUsing numbers: " << one << " and " << two << ", the larger one is: ";
if (one > two)
cout << one << endl;
else if (one < two)
cout << two << endl;
else
cout << "Neither of them! It's a draw." << endl;
cout << "\nUsing numbers: " << 13 << " and " << 84 << ", the larger one is: ";
if (13 > 84)
cout << 13 << endl;
else if (13 < 84)
cout << 84 << endl;
else
cout << "Neither of them! It's a draw." << endl;
int input1 = 0;
int input2 = 0;
cout << "\nPlease enter a number: ";
cin >> input1;
cout << "\nPlease enter a second number: ";
cin >> input2;
cout << "\nUsing numbers: " << input1 << " and " << input2 << ", the larger one is: ";
if (input1 > input2)
cout << input1 << endl;
else if (input1 < input2)
cout << input2 << endl;
else
cout << "Neither of them! It's a draw." << endl;
cout << "\n\tThank you for running me :3\n" << endl;
return 0;
}
You basically have to refactor the code to replace the duplicate code part in your main function.
If you look closely you will see that code like this repeats:
cout << "\nUsing numbers: " << nNum1 << " and " << nNum2 << ", the larger one is: ";
if (nNum1 > nNum2)
cout << nNum1 << endl;
else if (nNum1 < nNum2)
cout << nNum2 << endl;
else
cout << "Neither of them! It's a draw." << endl;
So put that into a function:
void CompareNumbers(int nNum1, int nNum2)
{
cout << "\nUsing numbers: " << nNum1 << " and " << nNum2 << ", the larger one is: ";
if (nNum1 > nNum2)
cout << nNum1 << endl;
else if (nNum1 < nNum2)
cout << nNum2 << endl;
else
cout << "Neither of them! It's a draw." << endl;
}
And call this in your main function instead of duplicating the said code block.
I am making a function to give the time taken to travel from Chicago to a certain city. I am trying to make it loop so that when the user chooses the city, it gives the time taken and loops back up to ask the main question and let the user choose another city. I am also including an option where they can exit the loop. What I have so far is this:
main()
{
TripInfo trip;
int choice;
do
{
cout << "You are in Chicago. Where would you like to drive?\n"
<< "Enter number of city\n" << "1. New York City\n" << "2. Boston\n"
<< "3. Philadelphia\n" << "4. Toronto\n" << "5. Washington D.C.\n"
<< "6. Miami\n" << "7. Indianapolis\n" << "8. Los Angeles\n"
<< "9. San Fransisco\n" << "10. Phoenix\n" << "11. EXIT" << endl;
cin >> choice;
if(choice = 11)
{
cout << "Program terminated." << endl;
break;
}
trip.setDistance(choice);
cout << "The distance from Chicago to " << trip.getDestination() << " is "
<< trip.getDistance() << endl;
trip.setRate();
cout << "The speed you will be travelling at from Chicago to "
<< trip.getDestination() << " is " << trip.getRate() << endl;
trip.calculateTime();
cout << "The time it will take to travel from Chicago to "
<< trip.getDestination() << " at " << trip.getRate()
<< " miles per hour will be:\n " << trip.getTime() << " hours."
<< endl;
}
}
The problem is in the output. Even though there is a condition for the if statement and if choice is not 11, the function still prints "Program terminated.". How do I fix this so that if choice = 11, the program terminates, and if choice is not 11, it continues and loops through the various functions again and again until choice is chosen to be 11?
You want choice == 11. A single = sign causes 11 to be assigned to choice (and that assignment evaluates to true).
You need to use == to compare for equality; = is assignment, returning the value assigned, and nonzero is interpreted as true.
A convention I've seen to try to prevent this issue is to put the constant on the left. The following block of code will produce a compiler error:
if(11 = choice)
{
cout << "Program terminated." << endl;
break;
}
if(choice = 11)
means you assign choice a value of 11, and test for if value is non-zero, which is true. It should be
if(choice == 11)
The correct format is
if(choice == 11) {
--- }
= is used for assignment and == is used for checking the equality.
Also you have to give a whilecondition at the end of do statement for checking the condition to enter in the loop again.
if (choice = 13) {......}
the expression is true ever, assignment expression value is var's value, above is choice, the assignment expression is 13, 13 is true.
you can write 13 = choice to protect error by compiler, but i suggest you write choice == 13 ways, because this ways will understand well.
working on one of my first programming assignments, a text to morse (and back) convertor, but for whatever reason when I introduce a piece of text with a space between words my programme goes into an endless loop and crashes. Any ideas? Sorry if this description sucks, still getting my head around programming lingo.
this is the piece of the program that isn't functioning properly:
{
string user_input;
cout << "----------------------------------------" <<endl
<< "Text to Morse Mode" << endl
<< "Enter text for conversion : "<<endl;
cin >> user_input;
cout << endl << endl << user_input << " converts to : ";
unsigned int str_lenght;
str_lenght=user_input.size();
cout << endl;
for (i=0;i<str_lenght;i++)
{
find_string=0;
while (find_string < stop_string)
{
if (user_input[i]==text[find_string][0])
{
count=1;
cout << morse[find_string] << " ";
break;
}
find_string = find_string+1;
}
}
cout << endl << endl << endl;
if (count==0)
cout << endl << " an error was encountered " << "\a" << endl ;
}
stop_string isn't defined anywhere from what I see. In order to break the loop via incrementing you need to define stop_string. Also find_string = find_string+1; could be shortened to find_string++
First you haven't defined stop_string variable anywhere. First define it or use another variable. If it is string length intent to use here, use the str_length you have created.
Secondly if you want to input spaces in between your words, use getline instead of cin. cin delimits space character.