Thread overview
How do you put log calls in constructors when they may be created in a static context?
Aug 08
aliak
Aug 09
aliak
Aug 09
aliak
Aug 09
aliak
Aug 10
Timoses
Aug 10
aliak
August 08
I'm trying to debug stuff, so I want to add verbose logging

struct S(T) {
  this() {
    writeln("created S(T) with properties and ID");
  }
}

static a = S!int(); // bah

I guess users can call this code from any context, but when i'd also like to see the log output for debugging purposes. Is there a way around this?

Can I maybe only do a writeln in a non compile-time context?

Cheers,
- ali
August 08
On Wednesday, August 8, 2018 3:54:34 PM MDT aliak via Digitalmars-d-learn wrote:
> I'm trying to debug stuff, so I want to add verbose logging
>
> struct S(T) {
>    this() {
>      writeln("created S(T) with properties and ID");
>    }
> }
>
> static a = S!int(); // bah
>
> I guess users can call this code from any context, but when i'd also like to see the log output for debugging purposes. Is there a way around this?
>
> Can I maybe only do a writeln in a non compile-time context?

if(__ctfe)
{
    // code here will execute if this is encountered during CTFE
}
else
{
    // code here will execute if this is encountered outside of CTFE
}

- Jonathan M Davis



August 09
On Wednesday, 8 August 2018 at 23:47:22 UTC, Jonathan M Davis wrote:
> On Wednesday, August 8, 2018 3:54:34 PM MDT aliak via Digitalmars-d-learn wrote:
>> I'm trying to debug stuff, so I want to add verbose logging
>>
>> struct S(T) {
>>    this() {
>>      writeln("created S(T) with properties and ID");
>>    }
>> }
>>
>> static a = S!int(); // bah
>>
>> I guess users can call this code from any context, but when i'd also like to see the log output for debugging purposes. Is there a way around this?
>>
>> Can I maybe only do a writeln in a non compile-time context?
>
> if(__ctfe)
> {
>     // code here will execute if this is encountered during CTFE
> }
> else
> {
>     // code here will execute if this is encountered outside of CTFE
> }
>
> - Jonathan M Davis

That won't work because __ctfe is not readable at compile time. And I don't want that writeln there when there's compile time evaluation because errors.

1) I want to be able to log when a type is created
2) I want to declare a locally static runtime type

Ie:

import std.stdio;

struct S(T) {
    T i;
    this(T i) {
        this.i = i;
        writeln("log it");
    }
}

int f() {
    static x = S!int(3);
    return x.i++;
}

void main() {
    writeln(f); // print 3
    writeln(f); // print 4
}



August 09
On Thursday, August 9, 2018 2:37:49 AM MDT aliak via Digitalmars-d-learn wrote:
> On Wednesday, 8 August 2018 at 23:47:22 UTC, Jonathan M Davis
>
> wrote:
> > On Wednesday, August 8, 2018 3:54:34 PM MDT aliak via
> >
> > Digitalmars-d-learn wrote:
> >> I'm trying to debug stuff, so I want to add verbose logging
> >>
> >> struct S(T) {
> >>
> >>    this() {
> >>
> >>      writeln("created S(T) with properties and ID");
> >>
> >>    }
> >>
> >> }
> >>
> >> static a = S!int(); // bah
> >>
> >> I guess users can call this code from any context, but when i'd also like to see the log output for debugging purposes. Is there a way around this?
> >>
> >> Can I maybe only do a writeln in a non compile-time context?
> >
> > if(__ctfe)
> > {
> >
> >     // code here will execute if this is encountered during CTFE
> >
> > }
> > else
> > {
> >
> >     // code here will execute if this is encountered outside of
> >
> > CTFE
> > }
> >
> > - Jonathan M Davis
>
> That won't work because __ctfe is not readable at compile time. And I don't want that writeln there when there's compile time evaluation because errors.

Huh? __ctfe's entire purpose is so that you can differentiate between code that's run at compile-time and code that's run at runtime. If a piece of code is executed at compile-time, __ctfe is true, whereas if it's executed at runtime, __ctfe is false. So, if you have

this(T i)
{
    if(!__ctfe)
        writeln("log it");
}

then the code will print "log it" if the object is constructed at runtime, whereas it won't print anything if it's run at compile time, and there won't be any errors for trying to call writeln at compile time, because it will have been skipped.

- Jonathan M Davis



August 09
On Thursday, 9 August 2018 at 12:01:42 UTC, Jonathan M Davis wrote:
> On Thursday, August 9, 2018 2:37:49 AM MDT aliak via Digitalmars-d-learn wrote:
>> On Wednesday, 8 August 2018 at 23:47:22 UTC, Jonathan M Davis
>>
>> wrote:
>> > On Wednesday, August 8, 2018 3:54:34 PM MDT aliak via
>> >
>> > Digitalmars-d-learn wrote:
>> >> I'm trying to debug stuff, so I want to add verbose logging
>> >>
>> >> struct S(T) {
>> >>
>> >>    this() {
>> >>
>> >>      writeln("created S(T) with properties and ID");
>> >>
>> >>    }
>> >>
>> >> }
>> >>
>> >> static a = S!int(); // bah
>> >>
>> >> I guess users can call this code from any context, but when i'd also like to see the log output for debugging purposes. Is there a way around this?
>> >>
>> >> Can I maybe only do a writeln in a non compile-time context?
>> >
>> > if(__ctfe)
>> > {
>> >
>> >     // code here will execute if this is encountered during CTFE
>> >
>> > }
>> > else
>> > {
>> >
>> >     // code here will execute if this is encountered outside of
>> >
>> > CTFE
>> > }
>> >
>> > - Jonathan M Davis
>>
>> That won't work because __ctfe is not readable at compile time. And I don't want that writeln there when there's compile time evaluation because errors.
>
> Huh? __ctfe's entire purpose is so that you can differentiate between code that's run at compile-time and code that's run at runtime. If a piece of code is executed at compile-time, __ctfe is true, whereas if it's executed at runtime, __ctfe is false. So, if you have
>
> this(T i)
> {
>     if(!__ctfe)
>         writeln("log it");
> }
>
> then the code will print "log it" if the object is constructed at runtime, whereas it won't print anything if it's run at compile time, and there won't be any errors for trying to call writeln at compile time, because it will have been skipped.
>
> - Jonathan M Davis

Maybe I'm just explaining what I'm trying to do wrong, but that code doesn't compile when "this" is called in a valid compile time evaluation context, you'll get errors: https://run.dlang.io/is/KiJrR1

That link contains the gist of what I want to do. If you could static if (__ctfe) ...  then that'd work but I don't know if there's something like that. Alternatively, if I can get a non compile time evaluated static then that also will do the trick.

August 09
On Thursday, August 9, 2018 7:15:58 AM MDT aliak via Digitalmars-d-learn wrote:
> On Thursday, 9 August 2018 at 12:01:42 UTC, Jonathan M Davis
>
> wrote:
> > On Thursday, August 9, 2018 2:37:49 AM MDT aliak via
> >
> > Digitalmars-d-learn wrote:
> >> On Wednesday, 8 August 2018 at 23:47:22 UTC, Jonathan M Davis
> >>
> >> wrote:
> >> > On Wednesday, August 8, 2018 3:54:34 PM MDT aliak via
> >> >
> >> > Digitalmars-d-learn wrote:
> >> >> I'm trying to debug stuff, so I want to add verbose logging
> >> >>
> >> >> struct S(T) {
> >> >>
> >> >>    this() {
> >> >>
> >> >>      writeln("created S(T) with properties and ID");
> >> >>
> >> >>    }
> >> >>
> >> >> }
> >> >>
> >> >> static a = S!int(); // bah
> >> >>
> >> >> I guess users can call this code from any context, but when i'd also like to see the log output for debugging purposes. Is there a way around this?
> >> >>
> >> >> Can I maybe only do a writeln in a non compile-time context?
> >> >
> >> > if(__ctfe)
> >> > {
> >> >
> >> >     // code here will execute if this is encountered during
> >> >
> >> > CTFE
> >> >
> >> > }
> >> > else
> >> > {
> >> >
> >> >     // code here will execute if this is encountered outside
> >> >
> >> > of
> >> >
> >> > CTFE
> >> > }
> >> >
> >> > - Jonathan M Davis
> >>
> >> That won't work because __ctfe is not readable at compile time. And I don't want that writeln there when there's compile time evaluation because errors.
> >
> > Huh? __ctfe's entire purpose is so that you can differentiate between code that's run at compile-time and code that's run at runtime. If a piece of code is executed at compile-time, __ctfe is true, whereas if it's executed at runtime, __ctfe is false. So, if you have
> >
> > this(T i)
> > {
> >
> >     if(!__ctfe)
> >
> >         writeln("log it");
> >
> > }
> >
> > then the code will print "log it" if the object is constructed at runtime, whereas it won't print anything if it's run at compile time, and there won't be any errors for trying to call writeln at compile time, because it will have been skipped.
> >
> > - Jonathan M Davis
>
> Maybe I'm just explaining what I'm trying to do wrong, but that code doesn't compile when "this" is called in a valid compile time evaluation context, you'll get errors: https://run.dlang.io/is/KiJrR1
>
> That link contains the gist of what I want to do. If you could static if (__ctfe) ...  then that'd work but I don't know if there's something like that. Alternatively, if I can get a non compile time evaluated static then that also will do the trick.

It's failing, because you got the condition backwards. __ctfe is true during CTFE and false during runtime. Your code has

if(__ctfe)
    writeln("log it");

which means that it will attempt to run writeln at compile time, whereas if you used

if(!__ctfe)
    writeln("log it");

it would skip it at compile time. The problem isn't that writeln is being compiled in. The problem is that it's being encountered when CTFE is running the code. So, a static if is unnecessary. You just need to get the condition right.

- Jonathan M Davis



August 09
On Thursday, 9 August 2018 at 20:02:41 UTC, Jonathan M Davis wrote:
> On Thursday, August 9, 2018 7:15:58 AM MDT aliak via Digitalmars-d-learn wrote:
>> [...]
>
> It's failing, because you got the condition backwards. __ctfe is true during CTFE and false during runtime. Your code has
>
> if(__ctfe)
>     writeln("log it");
>
> which means that it will attempt to run writeln at compile time, whereas if you used
>
> if(!__ctfe)
>     writeln("log it");
>
> it would skip it at compile time. The problem isn't that writeln is being compiled in. The problem is that it's being encountered when CTFE is running the code. So, a static if is unnecessary. You just need to get the condition right.
>
> - Jonathan M Davis

Haha doh! Backwards it was. Thanks!
August 10
On Wednesday, 8 August 2018 at 21:54:34 UTC, aliak wrote:
> I'm trying to debug stuff, so I want to add verbose logging
>
> struct S(T) {
>   this() {
>     writeln("created S(T) with properties and ID");
>   }
> }
>
> static a = S!int(); // bah
>
> I guess users can call this code from any context, but when i'd also like to see the log output for debugging purposes. Is there a way around this?
>
> Can I maybe only do a writeln in a non compile-time context?
>
> Cheers,
> - ali

How about debug [1]?

struct S()T {
    this() {
        debug { writeln("Created..."); }
    }
}

and compile with the debug flag. You can also specify a debug identifier or level.

[1]: https://dlang.org/spec/version.html#debug
August 10
On Friday, 10 August 2018 at 09:29:04 UTC, Timoses wrote:
> On Wednesday, 8 August 2018 at 21:54:34 UTC, aliak wrote:
>> I'm trying to debug stuff, so I want to add verbose logging
>>
>> struct S(T) {
>>   this() {
>>     writeln("created S(T) with properties and ID");
>>   }
>> }
>>
>> static a = S!int(); // bah
>>
>> I guess users can call this code from any context, but when i'd also like to see the log output for debugging purposes. Is there a way around this?
>>
>> Can I maybe only do a writeln in a non compile-time context?
>>
>> Cheers,
>> - ali
>
> How about debug [1]?
>
> struct S()T {
>     this() {
>         debug { writeln("Created..."); }
>     }
> }
>
> and compile with the debug flag. You can also specify a debug identifier or level.
>
> [1]: https://dlang.org/spec/version.html#debug

Very nice :D Thanks!