simple graphing calculator in c++ - edit line 27 and 28

graphingCalc.cpp

#include <chrono>
#include <cmath>
#include <iostream>
#include <string>
#include <vector>

constexpr uint32_t LENGTH = 120;
constexpr int HEIGHT = 28;

using Duration =
	std::chrono::duration<float, std::chrono::milliseconds::period>;
template <typename T>
static float time_diff(const std::chrono::time_point<T>& a,
					   const std::chrono::time_point<T>& b) {
	return Duration(a - b).count();
}

template <typename T>
static void get_input(T& value) {
	using streamsize = std::numeric_limits<std::streamsize>;

	if (std::cin.peek() != '\n') {
		while (!(std::cin >> value)) {
			printf("Invalid value!\n");
			std::cin.clear();
			std::cin.ignore(streamsize::max(), '\n');
		}
	}
	std::cin.ignore(streamsize::max(), '\n');
}

int main() {
	using std::chrono::system_clock;

	uint32_t length = LENGTH;
	printf("oat's graphing calculator tm!\nEnter graph length (%d): ", length);
	get_input(length);

	int height = HEIGHT;
	printf("Enter graph height (%d): ", height);
	get_input(height);

	printf("Ok! Hold on...\n");

	std::vector<float> vals(length);
	std::vector<float> vals2(length);

	// calculating
	const auto& calcStart = system_clock::now();
	for (uint32_t i = 1; i < length; i++) {
		float x = float(i) / length;

		float y = 0.3f / x;  // enter formula(s) here!
		float y2 = std::sqrt(x);

		vals[i] = y;
		vals2[i] = y2;
	}

	printf("Calculating took %.3fms\n\n",
		   time_diff(system_clock::now(), calcStart));

	// rendering (?)
	const auto& renderStart = system_clock::now();
	for (int y = height - 1; y >= 0; y--) {
		putchar('|');
		for (uint32_t x = 1; x < length; x++) {
			const bool firstRender = std::floor(vals[x] * height) == float(y);
			const bool secondRender = std::floor(vals2[x] * height) == float(y);

			if (firstRender || secondRender) {
				putchar(firstRender && secondRender ? '$' : '#');
			} else {
				putchar(y == 0 ? '-' : ' ');
			}
		}
		putchar('\n');
	}
	printf("Rendering took %.3fms",
		   time_diff(system_clock::now(), renderStart));
}