range.cpp

// This is an example of using the z::core::range() generator to generate a list of numbers.
// Ranges are a memory-efficient way of creating and looping over a large range.
// z::core::range(begin = 0, end, step = 1)
 
#include <iostream>
#include <z/core.hpp>
#include <z/system/sleep.hpp>
#include <z/util/progress.hpp>
 
using z::core::join;
using z::core::range;
using z::system::sleep;
 
int main() {
    // You can iterate over ranges just like arrays.
    "short range:"_zs.writeln(std::cout);
    for (auto i : range(6)) {
        (">"_zs + i).writeln(std::cout);
    }
 
    // To convert to an array, use the collect() method.
    auto list = range(15, 100, 5).collect();
    ("\narray: "_zs + join(list, ',')).writeln(std::cout);
 
    // Unlike arrays, you can create VERY long ranges with no memory impact.
    // An array of 1 trillion elements would take a long time to allocate, but the range is instant.
    "\nlong range:"_zs.writeln(std::cout);
    for (auto i : range(1'000'000'000)) {
        (">"_zs + i).writeln(std::cout);
        if (i > 3) {
            "Exiting early!"_zs.writeln(std::cout);
            break;
        }
    }
 
    // Skipping elements
    // Notice how the range is still instant, even though we're skipping 500,000 elements.
    "\nskipping some elements and limiting to 5 total:"_zs.writeln(std::cout);
    for (auto i : (range(1'000'000).forEach([](long) { sleep(100); })).skip(500'000).limit(5)) {
        (">"_zs + i).writeln(std::cout);
    }
 
    // Ranges can even be infinite!
    // This will loop forever, so best not to use it with functions that consume all values (e.g. `count()`).
    "\ninfinite range (only first 5):"_zs.writeln(std::cout);
    for (auto i : range(0, z::core::infinity).limit(5)) {
        (">"_zs + i).writeln(std::cout);
    }
 
    // A fun feature of generators is that they can have extra functionality bound to them.
    // Here, we are taking a long range, and binding a progress bar be updated while we iterate through it.
    z::util::progress progress;
    long max = 10'000'000;
    auto numbers = range(max).forEach([max, &progress](auto i) { progress.set(std::cout, i, max); });
 
    // See how here, we're not directly calling progress.set, but the progress bar displays!
    "\nSum a long range and display the progress:"_zs.writeln(std::cout);
    auto sum = numbers.reduce(0, std::plus<long>());
    ("Total: "_zs + sum).writeln(std::cout);
 
    return 0;
}