4 ms·

> The two missing pieces are - For three decades, many people have said "C++ is nearly usable, except for just one thing..." Many of those people have gotten t

> The two missing pieces are - For three decades, many people have said "C++ is nearly usable, except for just one thing..." Many of those people have gotten their way, which is why C++ is now a kitchen sink of mutually inoperable, poorly thought-out features, like someone implemented the entire index from Journal of Programming Language Design. If you don't believe me, check out the implementation of `flip` at the end of the article. Over a hundred lines of templates, variadic parameters, constexpr, r-value references, parameter forwarding, default and explicit constructors, and other things that, imho, simply should not exist in a modern programming language. So, instead, I'd say the best thing for C++, and the world, would, at this juncture to stop adding features.

jcelerier 1y ago
so how does flip looks like in your favourite language?
- hackyhacky 1y ago
  In Haskell it's: flip :: (a -> b -> c) -> b -> a -> c flip f x y = f y x A little better, I'd say. Note that the first line is the type signature and is technically optional. EDIT: and if that's too exotic for you, here's the solution in Python. def flip(x): return lambda *z: x(*reversed(z))
  - fooker 1y ago
    You misunderstand why the C++ version is complex. Here's a similar version in C++ that is a one liner too. https://godbolt.org/z/dhsdoGcc4 https://godbolt.org/z/dhsdoGcc4 Notably, examine the simple assembly generated. In comparison, most other languages doing this will not be able to optimize away these abstractions at all.
    - hackyhacky 1y ago
      I understand just fine why the C++ version is complex: it's because C++ is a poor language for higher-order function abstractions. Please don't make excuses for C++'s excessive inessential complexity: there is no reason why a programmer should need to concern themselves with "const r-values" and similar shenanigans in order to accomplish this simple task. The fact that the compiler is able to optimize away this code is a compiler issue, not a language issue. ghc will optimize away Haskell's flip and I didn't once have to write a compile-time index-reverser in template code.
      - fooker 1y ago
        > there is no reason why a programmer should need to concern themselves Agreed, hence my one liner version. > ghc will optimize away Haskell's flip Can you show me how? I am seeing 5000 lines of assembly. https://godbolt.org/z/KqTq5Ez5n https://godbolt.org/z/KqTq5Ez5n
        hackyhacky 1y ago
        The assembly is hard to understand. I recommend looking at the C-- intermediate output, using the -ddump-cmm flag, with -O2. The results in most of the functions getting inlined and flip is removed entirely. You can see this clearly if you use conspicuous numbers. If, instead of (flip foo 2 3), you give (flip foo 2 99), you will code like this: R3 = GHC.Types.[]_closure+1; R2 = 97; Sp = Sp - 16; call GHC.Show.$fShow(,)_itos'_info(R3, R2) args: 24, res: 0, upd: 24; 97 is calculated at compile time.

jcelerier 1y ago

so how does flip looks like in your favourite language?

hackyhacky 1y ago
In Haskell it's: flip :: (a -> b -> c) -> b -> a -> c flip f x y = f y x A little better, I'd say. Note that the first line is the type signature and is technically optional. EDIT: and if that's too exotic for you, here's the solution in Python. def flip(x): return lambda *z: x(*reversed(z))
- fooker 1y ago
  You misunderstand why the C++ version is complex. Here's a similar version in C++ that is a one liner too. https://godbolt.org/z/dhsdoGcc4 https://godbolt.org/z/dhsdoGcc4 Notably, examine the simple assembly generated. In comparison, most other languages doing this will not be able to optimize away these abstractions at all.
  - hackyhacky 1y ago
    I understand just fine why the C++ version is complex: it's because C++ is a poor language for higher-order function abstractions. Please don't make excuses for C++'s excessive inessential complexity: there is no reason why a programmer should need to concern themselves with "const r-values" and similar shenanigans in order to accomplish this simple task. The fact that the compiler is able to optimize away this code is a compiler issue, not a language issue. ghc will optimize away Haskell's flip and I didn't once have to write a compile-time index-reverser in template code.
    - fooker 1y ago
      > there is no reason why a programmer should need to concern themselves Agreed, hence my one liner version. > ghc will optimize away Haskell's flip Can you show me how? I am seeing 5000 lines of assembly. https://godbolt.org/z/KqTq5Ez5n https://godbolt.org/z/KqTq5Ez5n
      - hackyhacky 1y ago
        The assembly is hard to understand. I recommend looking at the C-- intermediate output, using the -ddump-cmm flag, with -O2. The results in most of the functions getting inlined and flip is removed entirely. You can see this clearly if you use conspicuous numbers. If, instead of (flip foo 2 3), you give (flip foo 2 99), you will code like this: R3 = GHC.Types.[]_closure+1; R2 = 97; Sp = Sp - 16; call GHC.Show.$fShow(,)_itos'_info(R3, R2) args: 24, res: 0, upd: 24; 97 is calculated at compile time.