Types(3) User Contributed Perl Documentation Types(3)NAMEPDL::Types - define fundamental PDL Datatypes
SYNOPSIS
use PDL::Types;
$pdl = ushort( 2.0, 3.0 );
print "The actual c type used to store ushort's is '" .
$pdl->type->realctype() . "'\n";
The actual c type used to store ushort's is 'unsigned short'
DESCRIPTION
Internal module - holds all the PDL Type info. The type info can be
accessed easily using the "PDL::Type" object returned by the type
method.
Skip to the end of this document to find out how to change the set of
types supported by PDL.
Support functions
A number of functions are available for module writers to get/process
type information. These are used in various places (e.g. "PDL::PP",
"PDL::Core") to generate the appropriate type loops, etc.
typesrtkeys
return array of keys of typehash sorted in order of type complexity
ppdefs
return array of pp symbols for all known types
typefld
return specified field ($fld) for specified type ($type) by querying
type hash
mapfld
map a given source field to the corresponding target field by querying
the type hash
typesynonyms
return type related synonym definitions to be included in pdl.h . This
routine must be updated to include new types as required. Mostly the
automatic updating should take care of the vital things.
PDL::Type OBJECTS
This module declares one class - "PDL::Type" - objects of this class
are returned by the type method of a piddle. It has several methods,
listed below, which provide an easy way to access type information:
Additionally, comparison and stringification are overloaded so that you
can compare and print type objects, e.g.
$nofloat = 1 if $pdl->type < float;
die "must be double" if $type != double;
For further examples check again the type method.
enum
Returns the number representing this datatype (see get_datatype).
symbol
Returns one of 'PDL_B', 'PDL_S', 'PDL_US', 'PDL_L', 'PDL_LL',
'PDL_F' or 'PDL_D'.
ctype
Returns the macro used to represent this type in C code (eg
'PDL_Long').
ppsym
The letter used to represent this type in PP code code (eg 'U' for
ushort).
realctype
The actual C type used to store this type.
shortctype
The value returned by "ctype" without the 'PDL_' prefix.
badvalue
Since PDL was compiled without support for 'bad' values, this
routine returns undef.
orig_badvalue
Since PDL was compiled without support for 'bad' values, this
routine returns undef.
Adding/removing types
You can change the types that PDL knows about by editing entries in the
definition of the variable @types that appears close to the top of the
file Types.pm.PL (i.e. the file from which this module was generated).
Format of a type entry
Each entry in the @types array is a hash reference. Here is an example
taken from the actual code that defines the "ushort" type:
{
identifier => 'US',
onecharident => 'U', # only needed if different from identifier
pdlctype => 'PDL_Ushort',
realctype => 'unsigned short',
ppforcetype => 'ushort',
usenan => 0,
packtype => 'S*',
},
Before we start to explain the fields please take this important
message on board: entries must be listed in order of increasing
complexity. This is critical to ensure that PDL"s type conversion works
correctly. Basically, a less complex type will be converted to a more
complex type as required.
Fields in a type entry
Each type entry has a number of required and optional entry.
A list of all the entries:
· identifier
Required. A short sequence of upercase letters that identifies this
type uniquely. More than three characters is probably overkill.
· onecharident
Optional. Only required if the "identifier" has more than one
character. This should be a unique uppercase character that will
be used to reference this type in PP macro expressions of the
"TBSULFD" type. If you don't know what I am talking about read the
PP manpage or ask on the mailing list.
· pdlctype
Required. The "typedefed" name that will be used to access this
type from C code.
· realctype
Required. The C compiler type that is used to implement this type.
For portability reasons this one might be platform dependent.
· ppforcetype
Required. The type name used in PP signatures to refer to this
type.
· usenan
Required. Flag that signals if this type has to deal with NaN
issues. Generally only required for floating point types.
· packtype
Required. The Perl pack type used to pack Perl values into the
machine representation for this type. For details see "perldoc -f
pack".
Also have a look at the entries at the top of Types.pm.PL.
The syntax is not written into stone yet and might change as the
concept matures.
Other things you need to do
You need to check modules that do I/O (generally in the IO part of the
directory tree). In the future we might add fields to type entries to
automate this. This requires changes to those IO modules first though.
You should also make sure that any type macros in PP files (i.e.
"$TBSULFD...") are updated to reflect the new type. PDL::PP::Dump has a
mode to check for type macros requiring updating. Do something like
find . -name \*.pd -exec perl -Mblib=. -M'PDL::PP::Dump=typecheck' {} \;
from the PDL root directory after updating Types.pm.PL to check for
such places.
perl v5.10.0 2008-08-29 Types(3)