Thread: convert integer to bool implicitly

How easy would it be to write a small type extension to have integer
automatically convert to bool?
For example, I want an implicit conversion that 0 is false and
everything else is true.

Is this C programming or can you do it with a local procedural language?

Thanks
Sim

Sim Zacks <sim@compulab.co.il> schrieb:

> How easy would it be to write a small type extension to have integer
> automatically convert to bool?
> For example, I want an implicit conversion that 0 is false and everything
> else is true.

test=# \d foo;
      Table "public.foo"
 Column |  Type   | Modifiers
--------+---------+-----------
 val    | integer |

test=# select * from foo;
 val
-----
   0
   1
   2
   3
(4 rows)

test=# select val::bool from foo;
 val
-----
 f
 t
 t
 t
(4 rows)


> Is this C programming or can you do it with a local procedural language?

You can use regular casts.


HTH, Andreas
--
Really, I'm not out to destroy Microsoft. That will just be a completely
unintentional side effect. (Linus Torvalds)
Kaufbach, Saxony, Germany, Europe.              N 51.05082°, E 13.56889°

I know I can do it explicitly, I need to do it implicitly.
I am having a problem with a Microsoft Access front-end , that uses -1
as true and 0 as false.
I have everything worked around all the places where I could find it by
using a cbool(), but this doesn't work with filters, which probably call
a "select where field =-1 or =0." automatically by access.

I get an ODBC error saying that "Operator does not exist: boolean=integer.

I would like to create the implicit conversion, so that it works both
without the cbool from now on, and that filters should work fine.
I have tried a number of different ODBC settings, and no matter what
setting there is always one problem or another that has to be overcome.
I can get it all to work if I put a Before Insert and Update trigger and
change the -1 to true, but I would have to do that for every boolean
field in my application. It would be a lot easier and make sense
system-wise to implicitly convert the integer to bool.

Andreas Kretschmer wrote:
> Sim Zacks <sim@compulab.co.il> schrieb:
>
>> How easy would it be to write a small type extension to have integer
>> automatically convert to bool?
>> For example, I want an implicit conversion that 0 is false and everything
>> else is true.
>
> test=# \d foo;
>       Table "public.foo"
>  Column |  Type   | Modifiers
> --------+---------+-----------
>  val    | integer |
>
> test=# select * from foo;
>  val
> -----
>    0
>    1
>    2
>    3
> (4 rows)
>
> test=# select val::bool from foo;
>  val
> -----
>  f
>  t
>  t
>  t
> (4 rows)
>
>
>> Is this C programming or can you do it with a local procedural language?
>
> You can use regular casts.
>
>
> HTH, Andreas

I got it working.
This has been bothering me for a long time, but now that it was listed
as an official bug in my system, I had to deal with it.

I'll post the solution under a new post, because I think this will help
a lot of people.

Sim Zacks wrote:
> I know I can do it explicitly, I need to do it implicitly.
> I am having a problem with a Microsoft Access front-end , that uses -1
> as true and 0 as false.
> I have everything worked around all the places where I could find it by
> using a cbool(), but this doesn't work with filters, which probably call
> a "select where field =-1 or =0." automatically by access.
>
> I get an ODBC error saying that "Operator does not exist: boolean=integer.
>
> I would like to create the implicit conversion, so that it works both
> without the cbool from now on, and that filters should work fine.
> I have tried a number of different ODBC settings, and no matter what
> setting there is always one problem or another that has to be overcome.
> I can get it all to work if I put a Before Insert and Update trigger and
> change the -1 to true, but I would have to do that for every boolean
> field in my application. It would be a lot easier and make sense
> system-wise to implicitly convert the integer to bool.
>
> Andreas Kretschmer wrote:
>> Sim Zacks <sim@compulab.co.il> schrieb:
>>
>>> How easy would it be to write a small type extension to have integer
>>> automatically convert to bool?
>>> For example, I want an implicit conversion that 0 is false and
>>> everything else is true.
>>
>> test=# \d foo;
>>       Table "public.foo"
>>  Column |  Type   | Modifiers
>> --------+---------+-----------
>>  val    | integer |
>>
>> test=# select * from foo;
>>  val
>> -----
>>    0
>>    1
>>    2
>>    3
>> (4 rows)
>>
>> test=# select val::bool from foo;
>>  val
>> -----
>>  f
>>  t
>>  t
>>  t
>> (4 rows)
>>
>>
>>> Is this C programming or can you do it with a local procedural language?
>>
>> You can use regular casts.
>>
>>
>> HTH, Andreas