• Tofu Ninja (15/15) Jun 03 2015 Is there a way other than exceptions for a called function to
• ketmar (2/4) Jun 03 2015 write mixin template for that. ;-)=
• Tofu Ninja (2/6) Jun 03 2015 Except mixin templates can only be used for declarations...
• ketmar (32/41) Jun 03 2015 you can cheat a compiler (warning! don't try that at home!):
• Artur Skawina via Digitalmars-d-learn (10/19) Jun 04 2015 Without a preprocessing step, you probably won't find anything

"Tofu Ninja" <emmons0 purdue.edu> writes:

Is there a way other than exceptions for a called function to 
force the caller to return?

Specifically, I know the return type of the caller(its always 
bool) and under certain circumstances I would like the caller to 
just give up and return false if the called function fails. With 
as little boiler plate as possible on the call site. In c++ I 
could do it very easily with macros, but I am failing to see a 
similar way to do it in D other than maybe string mixins but that 
seems like a bit much to do every time I want to call this thing.

I would be willing to put some boilerplate code in the beginning 
of the caller, I could just put that in a mixin.

I know exceptions are really what I should be using but they are 
such a pain to work with. I don't want to have to put try catch 
blocks every time I call the caller.

Any ideas?

ketmar <ketmar ketmar.no-ip.org> writes:

On Wed, 03 Jun 2015 22:37:52 +0000, Tofu Ninja wrote:

 I don't want to have to put try catch blocks every
 time I call the caller.

write mixin template for that. ;-)=

"Tofu Ninja" <emmons0 purdue.edu> writes:

On Thursday, 4 June 2015 at 01:01:08 UTC, ketmar wrote:
 On Wed, 03 Jun 2015 22:37:52 +0000, Tofu Ninja wrote:

 I don't want to have to put try catch blocks every
 time I call the caller.

 write mixin template for that. ;-)

Except mixin templates can only be used for declarations...

ketmar <ketmar ketmar.no-ip.org> writes:

On Thu, 04 Jun 2015 01:07:10 +0000, Tofu Ninja wrote:

 On Thursday, 4 June 2015 at 01:01:08 UTC, ketmar wrote:
 On Wed, 03 Jun 2015 22:37:52 +0000, Tofu Ninja wrote:

 I don't want to have to put try catch blocks every time I call the
 caller.

 write mixin template for that. ;-)

=20
 Except mixin templates can only be used for declarations...

you can cheat a compiler (warning! don't try that at home!):

  mixin template callit(alias fn) {
    private auto tmp () {
      try fn(); catch (Exception) {}
      return 0;
    }
    private auto tmpv =3D tmp();
  }

  void test (string s) {
    import std.stdio;
    writeln(s);
  }

  void main () {
    mixin callit!(() =3D> test("wow"));
    mixin callit!(() =3D> test("hey"));
  }


but actually, simple template will do the work too:

  template callit(alias fn, A...) {
    void callit (A args) {
      try fn(args); catch (Exception) {}
    }
  }

  void test (string s) {
    import std.stdio;
    writeln(s);
  }

  void main () {
    callit!test("wow");
    callit!test("hey");
  }
=

Artur Skawina via Digitalmars-d-learn <digitalmars-d-learn puremagic.com> writes:

On 06/04/15 00:37, Tofu Ninja via Digitalmars-d-learn wrote:
 Is there a way other than exceptions for a called function to force the caller
to return?
 
 Specifically, I know the return type of the caller(its always bool) and under
certain circumstances I would like the caller to just give up and return false
if the called function fails. With as little boiler plate as possible on the
call site. In c++ I could do it very easily with macros, but I am failing to
see a similar way to do it in D other than maybe string mixins but that seems
like a bit much to do every time I want to call this thing.
 
 I would be willing to put some boilerplate code in the beginning of the
caller, I could just put that in a mixin.
 
 I know exceptions are really what I should be using but they are such a pain
to work with. I don't want to have to put try catch blocks every time I call
the caller.
 
 Any ideas?

Without a preprocessing step, you probably won't find anything
that's much better than:

   enum caught(string C, string R = "typeof(return).init") =
      `try {`~C~`} catch return (`~R~`);`;

   bool f(int a) nothrow {
      mixin (caught!q{ code_that_throws(a); });
      return 1;
   }

artur