Re: [Firebird-devel] expanding SUBSTRING for FB1.5

[Arno B. <fir...@ab...>]

Hallo Ignacio,

> One thing i'm wonder from nay time ago y why substring only admits
> constants as string indexes, and i would like to know the reason why,
> because i'm planing to try to add expresions to this shortly..=20
>=20
> in detail i would like to change
>=20
> string_value_function :  SUBSTRING '(' value FROM pos_short_integer
> ')'
> | SUBSTRING '(' value FROM pos_short_integer FOR
> nonneg_short_integer ')'
>=20
> to
>=20
> string_value_function :  SUBSTRING '(' value FROM value ')'
> | SUBSTRING '(' value FROM value FOR value')'
>=20
> And tests numbers at runtime not at parse time.. perhaps is extatly =
this
> the reason why?

I thought it shouldn't be possible because the output describer-length =
was
calculated with the 'from' and 'for', but as far as i see this is not =
the case !
Then IMO should it be possible.
But when constants are given it's also possible to set a new output=20
describer length. Am i right with this ?

Example :
  AField has datatype varChar(50)
  SUBSTRING(AField FROM 1 FOR 10) =3D> should result in length 10=20
  instead of 50.

Regards,
Arno