4 ms·

The Expressive C++17 Coding Challenge in D

41 points by systems 9y ago

arunc 9y ago
This is a very well written article. The author shows an idiomatic D code and explains the details line by line. Clearly emphasizes the expressiveness of D.
shakna 9y ago
I always love how succinct D is, whilst still remaining fairly readable. I'd also like to point out that SafeD covers a fair bit of the language. Enough that I feel comfortable making it a requirement in production code.
typon 9y ago
This blog post was an amazing advertisement for D.
- geezerjay 9y ago
  I don't agree. The comparisons are rather disingenuous as the representative examples hand-picked for the other languages are rather crude and too much verbose. For instance, the 120-loc C++ program needlessly introduces functions that run a single loc (by adding 4 or 5 loc to the bill) and add a dozen or so lines by breaking long lines.
  - greenify 9y ago
    The C++ program won the challenge of being the "most expressive C++17" program for this task ...
    - geezerjay 9y ago
      ...and by "most expressive C++17 [program]" it actually meant this: > So the purpose of this challenge is to write a piece of code that contains as many features of C++17 as possible, and that is as clear as possible. ...which, clearly, states that the goal was not minimize lines of code. I bet D fanboys can find more apples-to-oranges comparisons where D comes out as the most citric alternative when compared with apples and bananas. And by the way, the contest was organized by a couple of blogs, and the winner was a self-confessed amateur. Hardly a tour de force in C++ programming.
dpc_pw 9y ago
D deserves much more popularity. It's much better language than Go, with many similiar strenghts. If only it had Google's backing... Eh... I still prefer Rust for many reasons (no exceptions, no GC, memory safety), but in my heart D is the second favourite - the more lightweight, expressive and pragmatic. I especially wish Rust had macro system and compilation times of D because they are the best in the class. :]
- systems 9y ago
  what i know is that d doesnt have a macro system but i has features that gives the same benefits, but using language constructs https://dlang.org/articles/pretod.html https://dlang.org/articles/pretod.html
kazinator 9y ago
TXR Lisp, using standard awk macro: (awk (:inputs *stdin*) (:set fs "," ofs ",") (:let pos (name [*args* 0]) (rplc [*args* 1])) ((= nr 1) (set pos (pos name f))) ((> nr 1) (set [f pos] rplc)) (t (prn))) Missing args -> pass through: $ txr solve.tl < data name,surname,city,country Adam,Jones,Manchester,UK Joe,Doe,Cracow,Poland Michael,Smith,Paris,France Alex,McNeil,Gdynia,Poland With args: $ txr solve.tl city London < data name,surname,city,country Adam,Jones,London,UK Joe,Doe,London,Poland Michael,Smith,London,France Alex,McNeil,London,Poland We need (:inputs stdin) so that awk takes its input from standard input rather than processing the city London arguments as input sources.
deleted 9y ago
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ncmncm 9y ago
Without looking at any other solutions, I whipped up a one-off 37-line C++11 program that is easily twice as fast as the best D or Rust one, with no special tricks. (Change out the uses of "auto" and it qualifies as C++98.) I am appalled that a 125-line program to do such a simple job could win. If that was the best they could do, I would have kept the challenge open until something better came in. I haven't tried the other programs on one-field files, or where the field selected is the first, or the last. Did you? #include <iostream> #include <fstream> #include <streambuf> #include <algorithm> #include <string> int main(int, char** argv) { std::ifstream in(argv[1]); std::string head; if (!(in >> head)) return std::cout << "input file missing\n", 1; head = "," + head + ","; auto sub = std::string(argv[3]); auto target = "," + std::string(argv[2]) + ","; auto pos = head.find(target); if (pos == std::string::npos) return std::cout << "column name doesn’t exists in the input file\n", 1; auto skip_pre = pos ? std::count(&head[0], &head[pos], ',') : 0; auto skip_post = std::count( &head[pos + target.size()], &head[head.size()], ','); std::ofstream out(argv[4]); auto ib = in.rdbuf(), ob = out.rdbuf(); ob->sputn(&head[1], head.size()-2); ob->sputc('\n'); bool skipping = pos == 0; for (int c = 0, count = skip_pre; (c = ib->snextc()) != EOF; ) { if (c == ',' || c == '\n') { if (skipping) { count = skip_post + skip_pre; skipping = count == 0; ob->sputn(&sub[0], sub.size()); } else if (--count == 0) { skipping = true; } ob->sputc(c); } else if (!skipping) ob->sputc(c); } }
- geezerjay 9y ago
  > I am appalled that a 125-line program to do such a simple job could win. The goal of that challenge was to pack the most C++17 features in a program, and it was just a challenge organized by a couple of blogs. The winner was also a self-confessed amateur. That's a telltale sign of how many people have participated, and the level of engagement that the challenge had.
test9753 9y ago
In Ocaml [LOC: 24] [Level: Beginner] open Core let () = if Array.length Sys.argv <> 5 then Printf.eprintf "Invalid args\nUsage: %s <input.csv> <column-name> <replacement-string> <output.csv>" Sys.argv.(0) else let input_file, column_name, replacement, output_file = Sys.argv.(1), Sys.argv.(2),Sys.argv.(3),Sys.argv.(4) in In_channel.with_file input_file ~f:(fun in_ch -> match In_channel.input_line in_ch with | None -> Printf.eprintf "Cannot read first line" | Some first_line -> let columns = String.split first_line ~on:',' in match List.findi columns ~f:(fun _ col -> col = column_name) with | None -> Printf.eprintf "Cannot find column: %s" column_name | Some (index, _) -> let _ = Out_channel.with_file output_file ~f:(fun out_ch -> Out_channel.output_string out_ch (first_line ^ "\n"); In_channel.fold_lines in_ch ~init:() ~f:(fun _ line -> let in_columns = String.split line ~on:',' in let out_columns = List.mapi ~f:(fun i col -> if i = index then replacement else col) in_columns in let out_line = (String.concat ~sep:"," out_columns) ^ "\n" in Out_channel.output_string out_ch out_line ) ) in ())

41 points by systems 9y ago

This is a very well written article. The author shows an idiomatic D code and explains the details line by line. Clearly emphasizes the expressiveness of D.

shakna 9y ago

I always love how succinct D is, whilst still remaining fairly readable. I'd also like to point out that SafeD covers a fair bit of the language. Enough that I feel comfortable making it a requirement in production code.

typon 9y ago

This blog post was an amazing advertisement for D.

geezerjay 9y ago
I don't agree. The comparisons are rather disingenuous as the representative examples hand-picked for the other languages are rather crude and too much verbose. For instance, the 120-loc C++ program needlessly introduces functions that run a single loc (by adding 4 or 5 loc to the bill) and add a dozen or so lines by breaking long lines.
- greenify 9y ago
  The C++ program won the challenge of being the "most expressive C++17" program for this task ...
  - geezerjay 9y ago
    ...and by "most expressive C++17 [program]" it actually meant this: > So the purpose of this challenge is to write a piece of code that contains as many features of C++17 as possible, and that is as clear as possible. ...which, clearly, states that the goal was not minimize lines of code. I bet D fanboys can find more apples-to-oranges comparisons where D comes out as the most citric alternative when compared with apples and bananas. And by the way, the contest was organized by a couple of blogs, and the winner was a self-confessed amateur. Hardly a tour de force in C++ programming.

dpc_pw 9y ago

D deserves much more popularity. It's much better language than Go, with many similiar strenghts. If only it had Google's backing... Eh... I still prefer Rust for many reasons (no exceptions, no GC, memory safety), but in my heart D is the second favourite - the more lightweight, expressive and pragmatic. I especially wish Rust had macro system and compilation times of D because they are the best in the class. :]

systems 9y ago
what i know is that d doesnt have a macro system but i has features that gives the same benefits, but using language constructs https://dlang.org/articles/pretod.html https://dlang.org/articles/pretod.html

kazinator 9y ago

TXR Lisp, using standard awk macro: (awk (:inputs *stdin*) (:set fs "," ofs ",") (:let pos (name [*args* 0]) (rplc [*args* 1])) ((= nr 1) (set pos (pos name f))) ((> nr 1) (set [f pos] rplc)) (t (prn))) Missing args -> pass through: $ txr solve.tl < data name,surname,city,country Adam,Jones,Manchester,UK Joe,Doe,Cracow,Poland Michael,Smith,Paris,France Alex,McNeil,Gdynia,Poland With args: $ txr solve.tl city London < data name,surname,city,country Adam,Jones,London,UK Joe,Doe,London,Poland Michael,Smith,London,France Alex,McNeil,London,Poland We need (:inputs stdin) so that awk takes its input from standard input rather than processing the city London arguments as input sources.

deleted 9y ago

[deleted]

deleted 9y ago

[deleted]

ncmncm 9y ago

Without looking at any other solutions, I whipped up a one-off 37-line C++11 program that is easily twice as fast as the best D or Rust one, with no special tricks. (Change out the uses of "auto" and it qualifies as C++98.) I am appalled that a 125-line program to do such a simple job could win. If that was the best they could do, I would have kept the challenge open until something better came in. I haven't tried the other programs on one-field files, or where the field selected is the first, or the last. Did you? #include <iostream> #include <fstream> #include <streambuf> #include <algorithm> #include <string> int main(int, char** argv) { std::ifstream in(argv[1]); std::string head; if (!(in >> head)) return std::cout << "input file missing\n", 1; head = "," + head + ","; auto sub = std::string(argv[3]); auto target = "," + std::string(argv[2]) + ","; auto pos = head.find(target); if (pos == std::string::npos) return std::cout << "column name doesn’t exists in the input file\n", 1; auto skip_pre = pos ? std::count(&head[0], &head[pos], ',') : 0; auto skip_post = std::count( &head[pos + target.size()], &head[head.size()], ','); std::ofstream out(argv[4]); auto ib = in.rdbuf(), ob = out.rdbuf(); ob->sputn(&head[1], head.size()-2); ob->sputc('\n'); bool skipping = pos == 0; for (int c = 0, count = skip_pre; (c = ib->snextc()) != EOF; ) { if (c == ',' || c == '\n') { if (skipping) { count = skip_post + skip_pre; skipping = count == 0; ob->sputn(&sub[0], sub.size()); } else if (--count == 0) { skipping = true; } ob->sputc(c); } else if (!skipping) ob->sputc(c); } }

geezerjay 9y ago
> I am appalled that a 125-line program to do such a simple job could win. The goal of that challenge was to pack the most C++17 features in a program, and it was just a challenge organized by a couple of blogs. The winner was also a self-confessed amateur. That's a telltale sign of how many people have participated, and the level of engagement that the challenge had.

test9753 9y ago

In Ocaml [LOC: 24] [Level: Beginner] open Core let () = if Array.length Sys.argv <> 5 then Printf.eprintf "Invalid args\nUsage: %s <input.csv> <column-name> <replacement-string> <output.csv>" Sys.argv.(0) else let input_file, column_name, replacement, output_file = Sys.argv.(1), Sys.argv.(2),Sys.argv.(3),Sys.argv.(4) in In_channel.with_file input_file ~f:(fun in_ch -> match In_channel.input_line in_ch with | None -> Printf.eprintf "Cannot read first line" | Some first_line -> let columns = String.split first_line ~on:',' in match List.findi columns ~f:(fun _ col -> col = column_name) with | None -> Printf.eprintf "Cannot find column: %s" column_name | Some (index, _) -> let _ = Out_channel.with_file output_file ~f:(fun out_ch -> Out_channel.output_string out_ch (first_line ^ "\n"); In_channel.fold_lines in_ch ~init:() ~f:(fun _ line -> let in_columns = String.split line ~on:',' in let out_columns = List.mapi ~f:(fun i col -> if i = index then replacement else col) in_columns in let out_line = (String.concat ~sep:"," out_columns) ^ "\n" in Out_channel.output_string out_ch out_line ) ) in ())