simonask/rx-ranges

rx::ranges is a minimalist ranges library for C++17

rx-ranges's Issues

Complete exception safety and noexcept hygiene

Currently, many functions are marked noexcept, despite potentially calling user-provided functions that may throw. The right thing to do is to add noexcept(noexcept(...)) syntax in those places.

The drawback is that it uglifies the code pretty significantly.

There are also probably places where unconditional noexcept can be safely added.

Make months in calendar constexpr

Discussion: ec88755#r36088781

But basically changing the definition of s_months_names to be constexpr and avoid the runtime cost.

Why is uniq a sink?

I would expect it to work like

RX_OPTIONAL<output_type> last_value;

uniq(…) {
    last_value.emplace(input.get());
    input.next();
}

constexpr void next() {
    while (!input.at_end()) {
        auto&& next_value = input.get();
        input.next();
        if (!eq(*last_value, next_value)) {
            last_value.emplace(std::forward<decltype(next_value)>(next_value));
            return;
        }
    }
    last_value.reset();
}

constexpr output_type get() const {
    return last_value;
}

missing include <stdexcept>

https://godbolt.org/z/3HB9h_

Test constexpr compatibility for all combinators

Currently, many things are marked constexpr that may or may not actually be usable in constexpr contexts due to the use of assertions. Whether assert() is usable in a constexpr context seems compiler-dependent.

Here is a solution for implementing assertions in constexpr contexts: https://akrzemi1.wordpress.com/2017/05/18/asserts-in-constexpr-functions/

VS2017 won't compile without Conformance Mode

As in the title. Not sure if can be marked as bug, but at least it's worth mentioning in the requirements.

Example Code and Console Output

#include "pch.h"
#include "ranges.hpp"
#include <iostream>
#include <vector>

template <typename Type>
struct Point {

    Point(Type x, Type y) noexcept
        : X { x }
        , Y { y }
    {
    }

    Type X;
    Type Y;
};

int main()
{
    std::vector<Point<int>> vec;
    vec.emplace_back(1, 2);
    vec.emplace_back(2, 3);
    vec.emplace_back(3, 4);

    auto transformed = vec
        | rx::filter([](Point<int> point) { return point.X == 3; })
        | rx::transform([](Point<int> point) { return point.X; })
        | rx::to_vector();

    for (auto x : transformed) {
        std::cout << x << '\n';
    }
}

1>c:\users\tomek\source\repos\consoleapplication7\consoleapplication7\ranges.hpp(1476): error C2133: 'vec': unknown size
1>c:\users\tomek\source\repos\consoleapplication7\consoleapplication7\ranges.hpp(235): note: see reference to function template instantiation 'auto rx::to_vector::operator ()<LHS>(R &&) const' being compiled
1>        with
1>        [
1>            LHS=rx::transform<main::<lambda_5eaf32db83d37af66b6c17510f1a5e05>>::Range<Inner>,
1>            R=rx::transform<main::<lambda_5eaf32db83d37af66b6c17510f1a5e05>>::Range<Inner>
1>        ]
1>c:\users\tomek\source\repos\consoleapplication7\consoleapplication7\ranges.hpp(1476): error C2512: 'std::vector<remove_cv<remove_reference<remove_cv<_Ty>::type::output_type>::type>::type,std::allocator<remove_cv<remove_reference<remove_cv<_Ty>::type::output_type>::type>::type>>': no appropriate default constructor available
1>        with
1>        [
1>            _Ty=remove_reference<unknown-type>::type
1>        ]
1>c:\users\tomek\source\repos\consoleapplication7\consoleapplication7\ranges.hpp(1476): note: see declaration of 'std::vector<remove_cv<remove_reference<remove_cv<_Ty>::type::output_type>::type>::type,std::allocator<remove_cv<remove_reference<remove_cv<_Ty>::type::output_type>::type>::type>>'
1>        with
1>        [
1>            _Ty=remove_reference<unknown-type>::type
1>        ]
1>c:\users\tomek\source\repos\consoleapplication7\consoleapplication7\ranges.hpp(1477): fatal error C1903: unable to recover from previous error(s); stopping compilation

First doesn't work after sort

As in the title, code below doesn't compile without calling to_vector() after sort

    std::vector<int> vec { 1, 2, 3, 4, 5 };

    auto firstItem = vec
        | rx::sort()
        | rx::first();

Remove default-constructibility requirement in ChainRange

https://github.com/simonask/rx-ranges/blob/develop/include/rx/ranges.hpp#L2053
_get should not call itself if sizeof...(rest) == 0.

transform is called twice on transform+filter

Hi!

Here dead simple example code:

#include <stdio.h>
#include <vector>
#include <rx/ranges.hpp>
int main()
{
  using namespace std;
  using namespace rx;
  vector<int> v = {1,2,3,4,5,6};
  auto r = v | rx::transform([](auto i){printf("tr=%d\n", i);return i*2;}) | filter([](auto i){return i>6;});
  for(auto i : r) {
    printf("for=%d\n", i);
  }
}

I noticed that once filter condition is true, tr= is printed twice for each for= output. IMO it's not really expected behaviour and looks like overhead.

RFE: string extension - split, strip, join

Hello.

I have some preliminary implementation split range, strip transform and join sink. But I'm not sure if they should be part of main lib or should be placed in a separate file as an optional extension.

strip takes two const iterators of input, two const iterators of separator and produces basic_string_view as output.
strip takes range of const CharT*, basic_string_view or basic_string as input and produces basic_string_view as output.
join takes range of const CharT*, basic_string_view or basic_string and const CharT*, basic_string_view or basic_string as input and produces basic_string as output.

Need to discuss this and I'll make corresponding PR.