Re: Filling an array at compile time
On Wednesday, 9 February 2022 at 16:37:22 UTC, Ali Çehreli wrote: On 2/9/22 01:07, bauss wrote: > It will not run at compile-time because csvText is a runtime variable. > It should be enum to be accessible at compile-time. Yes. For the sake of completeness, any expression needed at compile time will be (attempted to be) executed at compile time. For example, an expression used as a template parameter will be executed at compile time as well. > The append operation > will be executed at runtime, which means that even if the loop runs at > compile-time then you're effectively not winning anything and it > basically just becomes a loop-unroll manually done. That's not true. It all depends on how the expression is needed. If for example, the variable were defined as enum, the compiler had to execute the code at compile time to compute its value. > The solution would be to create a function that returns a string [...] > And then simply using mixin That is unnecessary and hurts readability. :/ Most programmers see string mixins as a last resort. In any case, some people may find a compile-time file parsing example that I included in a presentation: https://youtu.be/dRORNQIB2wA?t=3157 Ali Thank you Ali for the clarifications
Re: Filling an array at compile time
On 2/9/22 08:37, Ali Çehreli wrote: > In any case, some people may find a compile-time file parsing example > that I included in a presentation: That should mean "may find interesting". And I've just realized that the chapter link is off in that video. This is the beginning of that section: https://www.youtube.com/watch?v=dRORNQIB2wA&t=3065s Ali
Re: Filling an array at compile time
On 2/9/22 01:07, bauss wrote: > It will not run at compile-time because csvText is a runtime variable. > It should be enum to be accessible at compile-time. Yes. For the sake of completeness, any expression needed at compile time will be (attempted to be) executed at compile time. For example, an expression used as a template parameter will be executed at compile time as well. > The append operation > will be executed at runtime, which means that even if the loop runs at > compile-time then you're effectively not winning anything and it > basically just becomes a loop-unroll manually done. That's not true. It all depends on how the expression is needed. If for example, the variable were defined as enum, the compiler had to execute the code at compile time to compute its value. > The solution would be to create a function that returns a string [...] > And then simply using mixin That is unnecessary and hurts readability. :/ Most programmers see string mixins as a last resort. In any case, some people may find a compile-time file parsing example that I included in a presentation: https://youtu.be/dRORNQIB2wA?t=3157 Ali
Re: Filling an array at compile time
On Wednesday, 9 February 2022 at 10:25:34 UTC, bauss wrote: Is it guaranteed that the value is initialized at compiletime however? yes, D guarentees this at 100%.
Re: Filling an array at compile time
On Wednesday, 9 February 2022 at 10:01:15 UTC, Anonymouse wrote: On Wednesday, 9 February 2022 at 08:12:52 UTC, Vindex wrote: [...] I would do this. ``` import std; alias Record = Tuple!(string, string, string); static immutable string[][] table = () { string[][] table; string csvText = import("file.csv"); foreach (record; csvReader!Record(csvText)) { table ~= [record[0], record[1], record[2]]; } return table; }(); pragma(msg, table); // Available at compile-time void main() { writeln(table); } ``` And then `-J{path}` to tell the compiler where to find `file.csv`. ``` dmd -J. csv.d ``` Thanks! It does indeed work at compile time.
Re: Filling an array at compile time
On Wednesday, 9 February 2022 at 10:01:15 UTC, Anonymouse wrote: On Wednesday, 9 February 2022 at 08:12:52 UTC, Vindex wrote: Will the loop (foreach) run at compile time? How can I make it work at compile time? ``` import std.csv, std.stdio; alias Record = Tuple!(string, string, string); immutable string[][] table; shared static this() { string csvText = import("file.csv"); foreach (record; csvReader!Record(csvText)) { table ~= [record[0], record[1], record[2]]; } } void main() { writeln(table): } ``` I would do this. ``` import std; alias Record = Tuple!(string, string, string); static immutable string[][] table = () { string[][] table; string csvText = import("file.csv"); foreach (record; csvReader!Record(csvText)) { table ~= [record[0], record[1], record[2]]; } return table; }(); pragma(msg, table); // Available at compile-time void main() { writeln(table); } ``` And then `-J{path}` to tell the compiler where to find `file.csv`. ``` dmd -J. csv.d ``` Is it guaranteed that the value is initialized at compiletime however? Something being available at compiletime isn't the same as being initialized at compiletime only. If it's guaranteed then that's indeed the best solution.
Re: Filling an array at compile time
On Wednesday, 9 February 2022 at 08:12:52 UTC, Vindex wrote: Will the loop (foreach) run at compile time? How can I make it work at compile time? ``` import std.csv, std.stdio; alias Record = Tuple!(string, string, string); immutable string[][] table; shared static this() { string csvText = import("file.csv"); foreach (record; csvReader!Record(csvText)) { table ~= [record[0], record[1], record[2]]; } } void main() { writeln(table): } ``` I would do this. ``` import std; alias Record = Tuple!(string, string, string); static immutable string[][] table = () { string[][] table; string csvText = import("file.csv"); foreach (record; csvReader!Record(csvText)) { table ~= [record[0], record[1], record[2]]; } return table; }(); pragma(msg, table); // Available at compile-time void main() { writeln(table); } ``` And then `-J{path}` to tell the compiler where to find `file.csv`. ``` dmd -J. csv.d ```
Re: Filling an array at compile time
On Wednesday, 9 February 2022 at 08:12:52 UTC, Vindex wrote: Will the loop (foreach) run at compile time? How can I make it work at compile time? ``` import std.csv, std.stdio; alias Record = Tuple!(string, string, string); immutable string[][] table; shared static this() { string csvText = import("file.csv"); foreach (record; csvReader!Record(csvText)) { table ~= [record[0], record[1], record[2]]; } } void main() { writeln(table): } ``` It will not run at compile-time because csvText is a runtime variable. It should be enum to be accessible at compile-time. The second issue is that your foreach should probably be static foreach. The third issue is how you're creating "table". The append operation will be executed at runtime, which means that even if the loop runs at compile-time then you're effectively not winning anything and it basically just becomes a loop-unroll manually done. The solution would be to create a function that returns a string that is equivalent to the contents of the array you want to create, as if you wrote the content yourself. And then simply using mixin to "set" the value of the table by calling that function. Ex. ``` string getInt() { return "immutable a = 10;"; } mixin(getInt); // The variable a is accessible here ... ```
Filling an array at compile time
Will the loop (foreach) run at compile time? How can I make it work at compile time? ``` import std.csv, std.stdio; alias Record = Tuple!(string, string, string); immutable string[][] table; shared static this() { string csvText = import("file.csv"); foreach (record; csvReader!Record(csvText)) { table ~= [record[0], record[1], record[2]]; } } void main() { writeln(table): } ```
Re: Filling an array
On Saturday, 12 March 2016 at 18:33:16 UTC, Alex wrote: On Saturday, 12 March 2016 at 16:37:25 UTC, user42 wrote: On Saturday, 12 March 2016 at 14:33:19 UTC, Alex wrote: /snip I thought this was supposed to halt with an error rather than compile and set all members to 1. The syntax, to me anyways, doesn't really communicate the intention of: set all members to 1. //arr[] = 1; Whereas the following does fill(arr, 1); Well, this was not the question. As stated here: https://dlang.org/spec/arrays.html in the section "array setting", it is possible to set an array in such a manner. And my question was, why a specific array behaves not as expected. So, either there is a problem with filling an array, or, there is a problem with implicit conversion of a Nullable!T to its underlying type. Learned something new. I guess I missed that detail when I read that page.
Re: Filling an array
On Saturday, 12 March 2016 at 19:35:30 UTC, ag0aep6g wrote: On 12.03.2016 16:44, Mike Parker wrote: arr[] = cast(Nullable!uint)1; Nicer than a cast: construct a Nullable!int. arr[] = Nullable!uint(1); ok... so... this makes the error very strange, then... almost senseless...
Re: Filling an array
On 12.03.2016 16:44, Mike Parker wrote: arr[] = cast(Nullable!uint)1; Nicer than a cast: construct a Nullable!int. arr[] = Nullable!uint(1);
Re: Filling an array
On Saturday, 12 March 2016 at 16:37:25 UTC, user42 wrote: On Saturday, 12 March 2016 at 14:33:19 UTC, Alex wrote: /snip I thought this was supposed to halt with an error rather than compile and set all members to 1. The syntax, to me anyways, doesn't really communicate the intention of: set all members to 1. //arr[] = 1; Whereas the following does fill(arr, 1); Well, this was not the question. As stated here: https://dlang.org/spec/arrays.html in the section "array setting", it is possible to set an array in such a manner. And my question was, why a specific array behaves not as expected. So, either there is a problem with filling an array, or, there is a problem with implicit conversion of a Nullable!T to its underlying type.
Re: Filling an array
On Saturday, 12 March 2016 at 14:33:19 UTC, Alex wrote: /snip I thought this was supposed to halt with an error rather than compile and set all members to 1. The syntax, to me anyways, doesn't really communicate the intention of: set all members to 1. //arr[] = 1; Whereas the following does fill(arr, 1);
Re: Filling an array
On Saturday, 12 March 2016 at 15:44:00 UTC, Mike Parker wrote: On Saturday, 12 March 2016 at 14:33:19 UTC, Alex wrote: //arr[] = 1; The question is, why the commented out line throws the error: Error: cannot implicitly convert expression (1) of type int to Nullable!uint[], while the line after that works. Looks like a bug somewhere. The work around is to cast: arr[] = cast(Nullable!uint)1; I suggest you file this in the bug tracker [1] if it isn't there already. Just use he minimal code that shows the problem: void main() { import std.typecons; Nullable!uint[] arr; arr.length = 5; arr[] = 1; } [1] https://dlang.org/bugstats.php Thanks! Bug filed under https://issues.dlang.org/show_bug.cgi?id=15792
Re: Filling an array
On Saturday, 12 March 2016 at 14:33:19 UTC, Alex wrote: //arr[] = 1; The question is, why the commented out line throws the error: Error: cannot implicitly convert expression (1) of type int to Nullable!uint[], while the line after that works. Looks like a bug somewhere. The work around is to cast: arr[] = cast(Nullable!uint)1; I suggest you file this in the bug tracker [1] if it isn't there already. Just use he minimal code that shows the problem: void main() { import std.typecons; Nullable!uint[] arr; arr.length = 5; arr[] = 1; } [1] https://dlang.org/bugstats.php
Filling an array
Hi all! I have, maybe, a silly question.. Not sure, if https://forum.dlang.org/post/ibxhuqamgclrcatsy...@forum.dlang.org has something to do with the topic Having the following code: import std.typecons; import std.algorithm; void main() { uint[] arr_ref; arr_ref.length = 5; assert(arr_ref == [0, 0, 0, 0, 0]); arr_ref[] = 1; assert(arr_ref == [1, 1, 1, 1, 1]); Nullable!uint[] arr; arr.length = 5; bool[] check_arr; arr.each!(a => check_arr ~= a.isNull); assert(check_arr == [true, true, true, true, true]); //arr[] = 1; fill(arr, 1); assert(arr == [1, 1, 1, 1, 1]); } The question is, why the commented out line throws the error: Error: cannot implicitly convert expression (1) of type int to Nullable!uint[], while the line after that works.
Re: CTFE - filling an array
The Anh Tran wrote: static double[N] dd = void; dd is not a compile-time constant. static auto tmp = f!(N).fn(dd); The initializer of tmp must be a compile-time constant, but since dd is not a compile-time constant, you can't use CTFE on fn.
CTFE - filling an array
Hi, I would like to pre-create a double array, each element is calculated by a function. //- import std.stdio; import std.conv; import std.string; template f(int N) { bool fn(double[] tb) { for (int i = 1; i < N; i++) tb[i] = 1.0/i; return true; } } void main(string[] args) { const int N = 200; static double[N] dd = void; static auto tmp = f!(N).fn(dd); int n = toInt(args[1]); writefln("test array[%d] = %f", n, dd[n]); } //-- dmd.2021 says: cannot evaluate "static auto tmp = f!(N).fn(dd);" at compile-time. How can i fix it? Thanks.