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help with functions

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seeplus (6457)
@seeplus I got an error when I tried to implement that to my code..


As my post said, you need to compile as C++20 and your c++c20 compiler needs to have implemented concepts.
closed account (9G8M4G1T)
I see..

Can someone help me incorporate this? The examples I have look at to understand
returning the value have just confused me even more.


The three overloaded input functions look like this. (Provide the correct parameter type.):
1) char input(parameter_type prompt_text, parameter_type error_message_text); // for getting a letter
2) double input(parameter_type min_number, parameter_type max_number, parameter_type prompt_text,
parameter_type error_message_text); // for getting a number
3) void input(parameter_type x, parameter_type y, parameter_type prompt_text); // for getting a point (x, y)

For char, print the prompt; get a character. If the character is valid (a-z or A-Z) return it.
If it is NOT valid, display the error message and try again. Use isalpha() to verify the character
is alphabetic. Loop until a valid character is entered.


For the number, print the prompt. As part of the prompt,
print the acceptable range (min, max) allowed for the value.


Get a value. If it is within the range, return it.
If NOT valid, print the error message and try again.
Loop until a valid (within range) number is entered.
seeplus (6457)
Perhaps based upon previous code for function static:

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#include <iostream>
#include <cmath>
#include <string>

using namespace std;

enum Menu : char { letter = 'l', number = 'n', point = 'p', quit = 'q' };

Menu domenu() {
	char choice {};

	cout << "Options: " << letter << ")etter; " << number << ")umber; " << point << ")oint; " << quit << ")uit: ";
	cin >> choice;

	return static_cast<Menu>(choice);
}

void errorMessage() {
	cout << "This is not an option, try again!\n";
}

double distance(char c1, char c2) {
	return abs(c2 - c1);
}

double distance(double c1, double c2) {
	return abs(c2 - c1);
}

double distance(double x1, double y1, double x2, double y2) {
	return {sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2))};
}

void display(const string& msg, char c1, char c2) {
	static unsigned cnt {};

	cout << "(#" << ++cnt << ") " << msg << ' ' << c1
		<< " & " << c2 << " is: " << distance(c1, c2) << '\n';
}

void display(const string& msg, double d1, double d2) {
	static unsigned cnt {};

	cout << "(#" << ++cnt << ") " << msg << ' ' << d1
		<< " & " << d2 << " is: " << distance(d1, d2) << '\n';
}

void display(const string& msg, double x1, double y1, double x2, double y2) {
	static unsigned cnt {};

		cout << "(#" << ++cnt << ") " << msg << "("
		<< x1 << "," << y1 << ")" << " and ("
		<< x2 << "," << y2 << ") is: "
		<< distance(x1, y1, x2, y2) << " units.\n";
}

int main() {
	for (Menu userChoice {}; userChoice != quit; ) {
		switch (userChoice = domenu()) {
			case letter:
			{
				char c1 {}, c2 {};

				cout << "Enter first letter (a to z): ";
				cin >> c1;

				cout << "Enter second letter (a to z): ";
				cin >> c2;

				display("The distance between letters", c1, c2);
			}
				break;

			case number:
			{
				double x {}, y {};

				cout << "Enter first value (-100, 100): ";
				cin >> x;

				cout << "Enter second value (-200, 200): ";
				cin >> y;

				display("The units between", x, y);
			}
				break;

			case point:
			{
				double x1 {}, x2 {}, y1 {}, y2 {};

				cout << "Enter the first point (x1): ";
				cin >> x1;

				cout << "Enter the first point (y1): ";
				cin >> y1;

				cout << "Enter the second point (x2): ";
				cin >> x2;

				cout << "Enter the second point (y2): ";
				cin >> y2;

				display("The straight line distance between points", x1, y1, x2, y2);
			}
				break;

			case quit:
				cout << "Goodbye!\n";
				break;

			default:
				errorMessage();
				break;
		}
	}
}

Last edited on
closed account (9G8M4G1T)
thank you @seeplus

If anyone can help me with this error in my code where it only measures the distance correctly
when both letters are either entered in lowercase or uppercase:
Options: l)etter; n)umber; p)oint; q)uit: l
Enter first letter (a to z): A
Enter second letter (a to z): c
(#1) The distance between letters A & c is: 34


I have to add three overloaded distance functions that need to look like this:
1) int dist(char a, char b); // return the distance between two letters (a-z)
2) double dist(double d1, double d2); // return the distance between two numbers
3) double dist(double x1, double y1, double x2, double y2); // return distance between two points.

Which should fix the problem but I'm not sure where to add them
seeplus (6457)
For input functions and treating upper/lower case as the same, possibly:

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#include <iostream>
#include <cmath>
#include <string>
#include <limits>
#include <utility>
#include <cctype>

using namespace std;
using Point = std::pair<double, double>;

enum Menu : char { letter = 'l', number = 'n', point = 'p', quit = 'q' };

template<typename T = int>
auto getNum(const std::string& prm)
{
	const auto notsp {[&]() {while (std::isspace(static_cast<unsigned char>(std::cin.peek())) && std::cin.peek() != '\n') std::cin.ignore(); return std::cin.peek() != '\n'; }};
	T n {};

	while ((std::cout << prm) && (!(std::cin >> n) || notsp())) {
		std::cout << "Not a number\n";
		std::cin.clear();
		std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
	}

	std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
	return n;
}

std::string remzero(const std::string& str) {
	auto s(str);

	if (str.find('.')) {
		while (*s.rbegin() == '0')
			s.resize(s.size() - 1);

		if (*s.rbegin() == '.')
			s.resize(s.size() - 1);
	}

	return s;
}

char asUpper(char ch) {
	return static_cast<char>(std::toupper(static_cast<unsigned char>(ch)));
}

Menu domenu() {
	char choice {};

	cout << "Options: " << letter << ")etter; " << number << ")umber; " << point << ")oint; " << quit << ")uit: ";
	cin >> choice;

	return static_cast<Menu>(choice);
}

void errorMessage() {
	cout << "This is not an option, try again!\n";
}

double distance(char c1, char c2) {
	return abs(asUpper(c2) - asUpper(c1));
}

double distance(double c1, double c2) {
	return abs(c2 - c1);
}

double distance(const Point& p1, const Point& p2) {
	return {sqrt((p1.first - p2.first) * (p1.first - p2.first) + (p1.second - p2.second) * (p1.second - p2.second))};
}

void display(const string& msg, char c1, char c2) {
	static unsigned cnt {};

	cout << "(#" << ++cnt << ") " << msg << ' ' << c1
		<< " & " << c2 << " is: " << distance(c1, c2) << '\n';
}

void display(const string& msg, double d1, double d2) {
	static unsigned cnt {};

	cout << "(#" << ++cnt << ") " << msg << ' ' << d1
		<< " & " << d2 << " is: " << distance(d1, d2) << '\n';
}

void display(const string& msg, const Point& p1, const Point& p2) {
	static unsigned cnt {};

	cout << "(#" << ++cnt << ") " << msg << " ("
		<< p1.first << "," << p1.second << ")" << " and ("
		<< p2.first << "," << p2.second << ") is: "
		<< distance(p1, p2) << " units.\n";
}

char input(char, const std::string& inptxt, const std::string& errtxt) {
	char ch {};

	while ((std::cout << inptxt << " (a - z) : ") && (std::cin >> ch) && !std::isalpha(static_cast<unsigned char>(ch)))
		std::cout << errtxt << '\n';

	return ch;
}

double input(double, double minn, double maxn, const std::string& inptxt, const std::string& errtxt) {
	double no {};

	do {
		no = getNum<double>(inptxt + " (" + remzero(std::to_string(minn)) + ", " + remzero(std::to_string(maxn)) + ") : ");
	} while ((no < minn || no > maxn) && (std::cout << errtxt << '\n'));

	return no;
}

Point input(Point, const std::string& inptxt) {
	const auto x1 {getNum<double>(inptxt + " (x) : ")};
	const auto y1 {getNum<double>(inptxt + " (y) : ")};

	return {x1, y1};
}

int main() {
	for (Menu userChoice {}; userChoice != quit; ) {
		switch (userChoice = domenu()) {
			case letter:
			{
				static const auto letErr {"Not a letter"s};
				const auto c1 {input(char {}, "Enter first letter", letErr)};
				const auto c2 {input(char {}, "Enter second letter", letErr)};

				display("The distance between letters", c1, c2);
			}
			break;

			case number:
			{
				static const auto numErr {"Out of range"s};
				const auto x {input(double {}, -100, 100, "Enter first number", numErr)};
				const auto y {input(double {}, -200, 200, "Enter next number", numErr)};

				display("The units between", x, y);
			}
			break;

			case point:
			{
				const auto x {input(Point {}, "Enter the first point")};
				const auto y {input(Point {}, "Enter the second point")};

				display("The straight line distance between points", x, y);
			}
			break;

			case quit:
				cout << "Goodbye!\n";
				break;

			default:
				errorMessage();
				break;
		}
	}
}

Last edited on
JLBorges (13770)
> Can someone help me incorporate this?

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#include <string>
#include <iostream>
#include <cctype>

// 1) char input(parameter_type prompt_text, parameter_type error_message_text); // for getting a letter
//               (Provide the correct parameter type.)
char get_a_letter /* input */ ( const std::string& prompt, const std::string& error_message )
{
    std::cout << "prompt: " ; // print the prompt;

    char c ;
    std::cin >> c ; // get a character.

    // If the character is valid (a-z or A-Z) return it.
    // Use isalpha() to verify the character is alphabetic.
    if( std::isalpha( static_cast<unsigned char>(c) ) ) return c ;

    // invalid character
    // If it is NOT valid, display the error message
    std::cout << "*** error ***  " << error_message << '\n' ;
    return get_a_letter( prompt, error_message ) ; // and try again.
                                                   // (Loop until a valid character is entered.)
}

// Now try writing this on your own
// 2) double input(parameter_type min_number, parameter_type max_number, parameter_type prompt_text,
//                 parameter_type error_message_text); // for getting a number
// For the number, print the prompt. As part of the prompt,
// print the acceptable range (min, max) allowed for the value.
// Get a value. If it is within the range, return it.
// If NOT valid, print the error message and try again.
// Loop until a valid (within range) number is entered.
closed account (9G8M4G1T)
In the number option the range prints out as:

Enter first value (-100. - 100.) :
Enter second value (-200. - 200.) :

how can I change this and do I need a second error message since the range
is different?

it should look like this:

Enter first number (-100, 100):
Enter next number (-200, 200):
Last edited on
seeplus (6457)
Well to change - as a delim to , as a delim just change the - of L108 above to ,

[Above code changed to reflect this and the other wording changes etc etc.]
Last edited on
closed account (9G8M4G1T)
I was testing the code and noticed that it's not taking or displaying the input correctly for the point option

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Having this for x2 and y2 doesn't help. And the cout is correct but I can't find the error in the code..

Point input(Point, const std::string& inptxt) {
    const auto x1 {getNum<double>(inptxt + "(x) : ")};
    const auto y1 {getNum<double>(inptxt + "(y) : ")};

    return {x1, y1};



//Test output:

Options: l)etter; n)umber; p)oint; q)uit: p
Enter the first point (x) : 0
Enter the first point (y) : 3
Enter the second point (x) : 0
Enter the second point (y) : 4
(#1) The straight line distance between points(0,0) and (3,4) is: 1 units.
Last edited on
seeplus (6457)
Sorry, I messed up L69 when converting to Point. Changed above.
closed account (9G8M4G1T)
it is still printing the points incorrectly and I don't believe the error is in L69

could the error be in here?

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            case point:
            {
                // displays message for user input
                const auto x {input(Point {}, "Enter the first point")};
                const auto y {input(Point {}, "Enter the second point")};
                display("The straight line distance between points", x, y);
            }
Last edited on
seeplus (6457)
Ok. I didn't test properly. Mea Culpa. This is what happens you try to deal with multiple programs at once and have points called x and y. Doh........ Points are now called p1 and p2. Names do matter!


Options: l)etter; n)umber; p)oint; q)uit: p
Enter the first point (x) : 0
Enter the first point (y) : 3
Enter the second point (x) : 0
Enter the second point (y) : 4
(#1) The straight line distance between points (0,3) and (0,4) is: 1 units.
Options: l)etter; n)umber; p)oint; q)uit: p
Enter the first point (x) : 0
Enter the first point (y) : 3
Enter the second point (x) : 4
Enter the second point (y) : 0
(#2) The straight line distance between points (0,3) and (4,0) is: 5 units.
Options: l)etter; n)umber; p)oint; q)uit: q
Goodbye!

Last edited on
closed account (9G8M4G1T)
Ohh ok the error makes much more sense now. Thank you so much for all your help
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