On 10/4/06, Martin J. Evans <[EMAIL PROTECTED]> wrote:
With DBI/DBD::Oracle all values read from the database are scalars. As everyone will know, whether something read from the database is a string or a number in Perl purely depends on the context it is used in so:
internally, there are flags in the SV structure that hint as to what conversions have been done on the SV already, for efficiency's sake.
I have to admit I don't know how the JSON module knows what is a number and what is a string in Perl but I see the same issue with Data::Dumper so I presume there must be some way to find out if a perl scalar is a number or a string.
It seems like the pure perl Dumper tests values with a regex and optimizes to numbers when the stringification matches a number template, while the XS version checks the flags in the SV structure.
The problem gets a lot worse for me since I do some arithmetic on values pulled from the database before converting them to JSON and this is where Perl seems to change them into numbers e.g.
I don't want to have to do ($var +0) on all the number fields I pull from the database (to turn them into numbers) and neither do I want to do a '$var .= ""' (to turn all the fields into strings).
you might have to do exactly that. "$var" will produce a string version. Sorry. Apparently you can tell the JSON module to make everything strings: http://search.cpan.org/~makamaka/JSON-1.07/lib/JSON.pm#AUTOCONVERT
As an aside (and probably a perl question rather than a DBI one) does anyone know why the type of a scalar changes when you use it on the right side of an assignment: perl -MData::Dumper -le '$a="1"; print Dumper($a); $b += $a; print Dumper($a);' $VAR1 = '1'; $VAR1 = 1;
The has-been-evaluated-as-a-number flag got set on $a when it was evaluated as a number; then Dumper, with both available, chose the number format.
How does JSON and Data::Dumper know whether Perl thinks something is a number or a string?
inspecting the flags; except pure-perl Dumper apparently uses a regular expression to identify numbers. Those are guesses. The source is available for your inspection. -- The Country Of The Blind, by H.G. Wells http://cronos.advenge.com/pc/Wells/p528.html
