Re: map question
On Saturday, 22 January 2022 at 23:54:27 UTC, forkit wrote: On Saturday, 22 January 2022 at 19:55:43 UTC, Stanislav Blinov wrote: thanks for the explanation. That really helped :-) writeln( generate!(() => dice(0.6, 1.4)).take(howManyTimes) ); [1, 1, 1, 1, 0] (or after reading Ali's response - getting rid of rnd, and using _ ) writeln( howManyTimes.iota.map!(_ => dice(0.6, 1.4)) ); [1, 0, 1, 1, 1] They produce exactly the same thing, so I guess it comes down to personal choice now. Using `iota` here incurs additional computation and argument copies that are actually never used, i.e. wasted work. So I'd say go with `generate`, as that seems the intent.
Re: map question
On Sunday, 23 January 2022 at 09:08:46 UTC, Stanislav Blinov wrote: Using `iota` here incurs additional computation and argument copies that are actually never used, i.e. wasted work. So I'd say go with `generate`, as that seems the intent. Isn't this normally a compiler's job to eliminate all unused computations and copies? ```D auto foobar1(size_t n) { return n.iota.map!(_ => 123).array; } auto foobar2(size_t n) { return generate!(() => 123).take(n).array; } ``` LDC with "-O -release" command line options generates pretty much identical code for foobar1 and foobar2 (I'm only showing the main loop, but the rest is also the same): ``` 20: 48 39 c8cmp%rcx,%rax 23: 74 18 je 3d <_D2zz7foobar1FNaNbNfmZAi+0x3d> 25: c7 04 8a 7b 00 00 00movl $0x7b,(%rdx,%rcx,4) 2c: 48 83 c1 01 add$0x1,%rcx 30: 48 39 cbcmp%rcx,%rbx 33: 75 eb jne20 <_D2zz7foobar1FNaNbNfmZAi+0x20> ``` ``` 20: 48 39 c8cmp%rcx,%rax 23: 74 18 je 3d <_D2zz7foobar2FNaNbNfmZAi+0x3d> 25: c7 04 8a 7b 00 00 00movl $0x7b,(%rdx,%rcx,4) 2c: 48 83 c1 01 add$0x1,%rcx 30: 48 39 cbcmp%rcx,%rbx 33: 75 eb jne20 <_D2zz7foobar2FNaNbNfmZAi+0x20> ``` Do you have a better example to demonstrate `generate`'s superiority?
Re: map question
On Sunday, 23 January 2022 at 09:38:57 UTC, Siarhei Siamashka wrote: On Sunday, 23 January 2022 at 09:08:46 UTC, Stanislav Blinov wrote: Using `iota` here incurs additional computation and argument copies that are actually never used, i.e. wasted work. So I'd say go with `generate`, as that seems the intent. Isn't this normally a compiler's job to eliminate all unused computations and copies? It is the programmer's job long before it is the compiler's. It can do wonders on your "minimal" code but it's not its job to read your mind. ```D auto foobar1(size_t n) { return n.iota.map!(_ => 123).array; } auto foobar2(size_t n) { return generate!(() => 123).take(n).array; } ``` LDC with "-O -release" command line options generates pretty much identical code for foobar1 and foobar2 (I'm only showing the main loop, but the rest is also the same): ``` 20: 48 39 c8cmp%rcx,%rax 23: 74 18 je 3d <_D2zz7foobar1FNaNbNfmZAi+0x3d> 25: c7 04 8a 7b 00 00 00movl $0x7b,(%rdx,%rcx,4) 2c: 48 83 c1 01 add$0x1,%rcx 30: 48 39 cbcmp%rcx,%rbx 33: 75 eb jne20 <_D2zz7foobar1FNaNbNfmZAi+0x20> ``` ``` 20: 48 39 c8cmp%rcx,%rax 23: 74 18 je 3d <_D2zz7foobar2FNaNbNfmZAi+0x3d> 25: c7 04 8a 7b 00 00 00movl $0x7b,(%rdx,%rcx,4) 2c: 48 83 c1 01 add$0x1,%rcx 30: 48 39 cbcmp%rcx,%rbx 33: 75 eb jne20 <_D2zz7foobar2FNaNbNfmZAi+0x20> ``` Do you have a better example to demonstrate `generate`'s superiority? Try actual work instead of returning a literal :) Like e.g. calling dice(50, 50). One thing to note though - `generate` will always eagerly call its function at least once. Which of course should also be considered in choosing the desired implementation. I.e. if your `n` comes from user and is allowed to be 0, then `generate` becomes an inferior choice.
dynamic format specifier possible?
I would like to calculate the width of the format specifier dynamically, at runtime. e.g int WIDTH = something.length; then my format specifier would be: %WIDTHs instead of %9s // --- module test; import std; void main() { int val = 999000; writefln("[%9s]", val); // [ 999000] } // ---
Re: dynamic format specifier possible?
On 1/23/22 13:59, forkit wrote: I would like to calculate the width of the format specifier dynamically, at runtime. You use an asterisk and provide the width as an argument. This one uses the length of the name of the program: import std; void main(string[] args) { int val = 999000; writefln("[%*s]", args.front.length, val); // [ 999000] } Ali
Re: dynamic format specifier possible?
On Sunday, 23 January 2022 at 22:08:28 UTC, Ali Çehreli wrote: You use an asterisk and provide the width as an argument. This one uses the length of the name of the program: import std; void main(string[] args) { int val = 999000; writefln("[%*s]", args.front.length, val); // [ 999000] } Ali perfect! thanks.