4 ms·

What's the difference between this and something like python-esque generators which also appear to be lazy and have a much saner syntax? Doesn't C++ plan to sup

What's the difference between this and something like python-esque generators which also appear to be lazy and have a much saner syntax? Doesn't C++ plan to support coroutines which should provide a similar way to lazily evaluate lists? Also the example has a lot of boilerplate code that reminds me of template metaprogramming hell. Is this something that's expected to be wrapped up nicely by Boost & co. for end users?

mikeloomis 8y ago
A c++20 range is just a bounded container. instead of having to write, `(container.begin(), container.end())` for any function that uses iterators to bound itself, you just write `(container)` and it knows its a range. The range function in python is similar only in name, the c++20 range concept is not a generator. 2. There is a coroutine feature branch, I believe developed by Gor Nishanov, https://github.com/GorNishanov https://github.com/GorNishanov. Also not related to c++20 ranges. 3. Eric Niebler used a single templated function. This is not anywhere close to template metaprogramming hell, and I think you should look into templates as once you learn about them they become way less intimidating. Also has nothing to do with c++20 ranges.
- amelius 8y ago
  I have yet to see a non-managed systems programming language which supports coroutines properly. Rust supports async/await, but it's not the same thing, as this comment illustrates: https://news.ycombinator.com/item?id=15121199 https://news.ycombinator.com/item?id=15121199
  - mikeloomis 8y ago
    It'll be after 20 for sure, we're still waiting for the executor TS for async networking to be able to come in.
Sharlin 8y ago
The "for_each" (aka flatmap, or bind, or =<<), "maybe_view", and "yield_if" are basically a DSL for writing (admittedly ugly) lazy list comprehensions (generator expressions in Python or for comprehensions in Scala) in C++ without special language support for them. You're not supposed to have to implement these sorts of building blocks yourself, but they're not voted into the standard either at this point.
mattnewport 8y ago
Unlike Python, this compiles to pretty optimally efficient code.

mikeloomis 8y ago

A c++20 range is just a bounded container. instead of having to write, `(container.begin(), container.end())` for any function that uses iterators to bound itself, you just write `(container)` and it knows its a range. The range function in python is similar only in name, the c++20 range concept is not a generator. 2. There is a coroutine feature branch, I believe developed by Gor Nishanov, https://github.com/GorNishanov https://github.com/GorNishanov. Also not related to c++20 ranges. 3. Eric Niebler used a single templated function. This is not anywhere close to template metaprogramming hell, and I think you should look into templates as once you learn about them they become way less intimidating. Also has nothing to do with c++20 ranges.

amelius 8y ago
I have yet to see a non-managed systems programming language which supports coroutines properly. Rust supports async/await, but it's not the same thing, as this comment illustrates: https://news.ycombinator.com/item?id=15121199 https://news.ycombinator.com/item?id=15121199
- mikeloomis 8y ago
  It'll be after 20 for sure, we're still waiting for the executor TS for async networking to be able to come in.

Sharlin 8y ago

The "for_each" (aka flatmap, or bind, or =<<), "maybe_view", and "yield_if" are basically a DSL for writing (admittedly ugly) lazy list comprehensions (generator expressions in Python or for comprehensions in Scala) in C++ without special language support for them. You're not supposed to have to implement these sorts of building blocks yourself, but they're not voted into the standard either at this point.

mattnewport 8y ago

Unlike Python, this compiles to pretty optimally efficient code.