From: | Pedro Miguel Frazao Fernandes Ferreira <pfrazao(at)ualg(dot)pt> |
---|---|
To: | Peter Eisentraut <peter_e(at)gmx(dot)net> |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: float output precision questions |
Date: | 2002-10-30 10:22:01 |
Message-ID: | 3DBFB2C9.3090906@ualg.pt |
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Lists: | pgsql-hackers |
Peter Eisentraut wrote:
>
>>Matlab has a toolbox fucntion, claiming maximum precision, to convert
>>from its double type (PostgreSQL float8) to string which does a
>>sprintf('%25.18g',number).
>
>
> Do we have some mathematical guarantee that this is sufficient and
> necessary? If so, then it might do.
It is necessary if you want to do this type of (huge amount of number
storage) application:
[Some client] (insert) [PostgreSQL] (query) [Some client]
(double number a)-------->(float8 number)------->(double number b)
In order for a=b this is necessary. With current float8 output this is
not allways true.
Here is the help for that particular Matlab function:
NUM2MSTR Convert number to string in maximum precision.
S = NUM2MSTR(N) converts real numbers of input
matrix N to string output vector S, in
maximum precision.
See also NUM2STR.
If you want I can try to contact the guys who coded this function to know
if this is sufficient.
Thanks,
Pedro M. Ferreira
--
----------------------------------------------------------------------
Pedro Miguel Frazao Fernandes Ferreira
Universidade do Algarve
Faculdade de Ciencias e Tecnologia
Campus de Gambelas
8000-117 Faro
Portugal
Tel./Fax: (+351) 289 800950 / 289 819403
http://w3.ualg.pt/~pfrazao
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