exercise.cpp

// NOTE: Min C++ lang version is C++20. Make sure your project is set to that!

#include <iostream>
#include <vector>
#include <format>
#include <stdexcept>
#include <string>
#include <cassert>

using std::cout, std::cin, std::endl;

/// <summary>
/// Presents a menu asking the user to select from a set of options, of form:
/// ```
///		Select one:
///		1) Foo.
///		2) Bar.
///		3) Baz.
///		> 
/// ```
/// </summary>
/// <param name="opts">List of options to use.</param>
/// <returns>The menu option selected.</returns>
int present_menu(std::vector<std::string> opts) {
	assert(opts.size() > 0);

	int selection = -1; // VS demands an initializer, but it gets immediately overwritten a few lines from now.

	do {
		cout << "Select one:" << endl;
		for (auto i = 0; i < opts.size(); i++)
		{
			cout << std::format("{}) {}", i + 1, opts[i]) << endl;
		}
		cout << "> " << std::flush;

		cin >> selection;
		if (cin.fail()) {
			cin.clear(); // Quit failing.
			cin.ignore(INT32_MAX, '\n'); // And drain the buffer.
			selection = -1;
			continue;
		}
		selection--;
	} while (selection < 0 || selection >= opts.size());

	return selection;
}

/// <summary>
/// Different formats the prompt function can use
/// </summary>
enum PromptFormat {
	PromptFormat_Entry, // Enter a {}:
	PromptFormat_Direct, // {}
};

/// <summary>
/// Prompt the user for a value.
/// </summary>
/// <typeparam name="T">The value type being prompted for. Must work with std::cin.</typeparam>
/// <param name="prompt">The prompt to use</param>
/// <param name="form">The "form" for the prompt, see PromptFormat for details.</param>
/// <returns>The value entered.</returns>
template <typename T>
T prompt(std::string prompt, PromptFormat form = PromptFormat_Entry) {
	switch (form) {
	case PromptFormat_Entry:
		cout << std::format("Enter a {}: ", prompt);
		break;
	case PromptFormat_Direct:
		cout << prompt;
	default:
		throw new std::invalid_argument("form");
	}

	T value;
	cin >> value;
	return value;
}

int main()
{
    int x = 'crab';
	cout << std::format("{:X}", x) << endl;

	auto selected = present_menu({ "inches to feet", "feet to inches" });
	cout << endl;
	auto value = prompt<int>("integer in inches");

	switch (selected) {
	case 0: // inches->feet
		cout << std::format("{} inches is {} feet", value, value / 12.0f) << endl;
		break;
	case 1:
		cout << std::format("{} feet is {} inches", value, value * 12) << endl;
		break;
	}
}