• Abby (8/8) Mar 22 2020 Is there a way to create a template that would do the same is glib
• Dennis (13/24) Mar 22 2020 Sounds a lot like:
• Steven Schveighoffer (5/22) Mar 22 2020 I think it's essentially the D way to do that, but it appears that the
• Mike Parker (23/32) Mar 22 2020 The documentation for the function reads:
• Mike Parker (7/13) Mar 22 2020 Heh, of course, as Dennis pointed out, that's essentialy

Abby <loniro7678 twit-mail.com> writes:

Is there a way to create a template that would do the same is glib

g_return_val_if_fail() 
(https://developer.gnome.org/glib/stable/glib-Warnings-and-Assertions.html#g-return-val-if-fail)

I was hoping something like this would work

template returnValIfFail(alias expr, alias val)
{
     if(expr) return val;
}

Dennis <dkorpel gmail.com> writes:

On Sunday, 22 March 2020 at 18:48:32 UTC, Abby wrote:
 Is there a way to create a template that would do the same is 
 glib

 g_return_val_if_fail() 
 (https://developer.gnome.org/glib/stable/glib-Warnings-and-Assertions.html#g-return-val-if-fail)

I'm not famililar with glib, but the description:

 If expr evaluates to FALSE, the current function should be 
 considered to have undefined behaviour (a programmer error).

Sounds a lot like:

```
assert(expr);
```

 I was hoping something like this would work

 template returnValIfFail(alias expr, alias val)
 {
     if(expr) return val;
 }

It would have to be a string mixin, you can't inject a return 
statement otherwise.
The thing is, why do you want that? It seems shorter to just 
write it out:

if(expr) return val;
debug if(expr) return val;
returnValIfFail!(expr, val);

Steven Schveighoffer <schveiguy gmail.com> writes:

On 3/22/20 3:04 PM, Dennis wrote:
 On Sunday, 22 March 2020 at 18:48:32 UTC, Abby wrote:
 Is there a way to create a template that would do the same is glib

 g_return_val_if_fail() 
 (https://developer.gnome.org/glib/stable/glib-Warnings-and-Assertions.html#g
return-val-if-fail) 

 
 I'm not famililar with glib, but the description:
 
 If expr evaluates to FALSE, the current function should be considered 
 to have undefined behaviour (a programmer error).

 
 Sounds a lot like:
 
 ```
 assert(expr);
 ```

I think it's essentially the D way to do that, but it appears that the 
behavior of glib is to return a value instead.

The exact behavior there is not reproducible in D AFAIK without mixins.

-Steve

Mike Parker <aldacron gmail.com> writes:

On Sunday, 22 March 2020 at 18:48:32 UTC, Abby wrote:
 Is there a way to create a template that would do the same is 
 glib

 g_return_val_if_fail() 
 (https://developer.gnome.org/glib/stable/glib-Warnings-and-Assertions.html#g-return-val-if-fail)

 I was hoping something like this would work

 template returnValIfFail(alias expr, alias val)
 {
     if(expr) return val;
 }

The documentation for the function reads:

"If expr evaluates to FALSE, the current function should be 
considered to have undefined behaviour (a programmer error). The 
only correct solution to such an error is to change the module 
that is calling the current function, so that it avoids this 
incorrect call."

Looks like the best approach in D would be to return val when 
expr is true and assert(0) otherwise. Also, you'll probably want 
the args to be available at runtime, else it would be a very 
restrictive template. Perhaps something like this?

```
T returnValIfFail(T)(bool expr, T val) {
     if(expr) return val;
     else assert(0);
}

void main() {
     import std.stdio : writeln;
     int y = 10;
     int x = returnValIfFail(y >= 10, 20);
     writeln(x);
}
```

Mike Parker <aldacron gmail.com> writes:

On Sunday, 22 March 2020 at 19:04:40 UTC, Mike Parker wrote:

 ```
 T returnValIfFail(T)(bool expr, T val) {
     if(expr) return val;
     else assert(0);
 }

 ```

Heh, of course, as Dennis pointed out, that's essentialy 
assert(expr).

```
assert(expr);
x = val;
```