PDL::Types - define fundamental PDL Datatypes

 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'

Internal module - holds all the PDL Type info. The type info can be accessed easily using the CWPDL::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.

A number of functions are available for module writers to get/process type information. These are used in various places (e.g. CWPDL::PP, CWPDL::Core) to generate the appropriate type loops, etc.

return array of keys of typehash sorted in order of type complexity

return array of pp symbols for all known types

return specified field (CW$fld) for specified type (CW$type) by querying type hash

map a given source field to the corresponding target field by querying the type hash

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.

This module declares one class - CWPDL::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 CWctype without the 'PDL_' prefix.

badvalue

Returns the value used to indicate a missing (or bad) element for the given data type. See the badvalue routine in PDL::Bad for more details.

orig_badvalue

Returns the original value used to represent bad values for a given type. See the orig_badvalue routine in PDL::Bad for more details.

You can change the types that PDL knows about by editing entries in the definition of the variable CW@types that appears close to the top of the file Types.pm.PL (i.e. the file from which this module was generated).

Each entry in the CW@types array is a hash reference. Here is an example taken from the actual code that defines the CWushort 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.

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 CWidentifier 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 CWTBSULFD type. If you don't know what I am talking about read the PP manpage or ask on the mailing list.

•

pdlctype Required. The CWtypedefed 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 CWperldoc -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.

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. CW$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.