Scroll to navigation

Types(3pm) User Contributed Perl Documentation Types(3pm)


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 "PDL::Type" object returned by the type method as shown in the synopsis.

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. "PDL::PP", "PDL::Core") to generate the appropriate type loops, etc.


Returns an array of keys of typehash sorted in order of type complexity

 pdl> @typelist = PDL::Types::typesrtkeys;
 pdl> print @typelist;


Returns an array of pp symbols for all real types. This informs the default "GenericTypes" for "pp_def" functions, making support for complex types require an "opt-in".

 pdl> print PDL::Types::ppdefs
 B S U L N Q F D


Returns an array of pp symbols for all complex types.

 pdl> print PDL::Types::ppdefs_complex
 G C


Returns an array of pp symbols for all types including complex.

 pdl> print PDL::Types::ppdefs_all
 B S U L N Q F D G C


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.


As of 2.065, PDL supports these types:

Signed 8-bit value.
Unsigned 8-bit value.
Signed 16-bit value.
Unsigned 16-bit value.
Signed 32-bit value.
Unsigned 32-bit value.
Signed value, same size as a pointer on the system in use.
Signed 64-bit value.
Unsigned 64-bit value.
IEEE 754 <> single-precision real floating-point value.
IEEE 754 double-precision real value.
A C99 "long double", defined as "at least as precise as a double", but often more precise.
A C99 complex single-precision floating-point value.
A C99 complex double-precision floating-point value.
A C99 complex "long double" - see above for description.


This module declares one class - "PDL::Type" - objects of this class are returned by the type method of an ndarray. 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.

Returns the number representing this datatype (see get_datatype).
Returns one of 'PDL_B', 'PDL_S', 'PDL_US', 'PDL_L', 'PDL_IND', 'PDL_LL', 'PDL_F' or 'PDL_D'.
Returns the macro used to represent this type in C code (eg 'PDL_Long').
Synonym for "ctype".
The letter used to represent this type in PP code (eg 'U' for ushort).
The actual C type used to store this type.
The value returned by "ctype" without the 'PDL_' prefix.
The special numerical value used to represent bad values for this type. See "badvalue" in PDL::Bad for more details.
Given a string representing a C value, will return a C expression for this type that indicates whether that value is NaN (for complex values, if either is NaN).
Given a string representing a C value, will return a C expression for this type that indicates whether that value is finite (for complex values, if both are finite).
The string appended to floating-point functions for this floating-point type. Dies if called on non-floating-point type.
The default special numerical value used to represent bad values for this type. (You can change the value that represents bad values for each type during runtime.) See the orig_badvalue routine in PDL::Bad for more details.
Returns the appropriate "bswap*" from PDL::IO::Misc for the size of this type, including a no-op for types of size 1. Note this means a one-line construction means you must call the return value:

Returns whether the type is real-only (true) or can hold complex values (false).

  die "Real data only!" if !$pdl->type->real;
Returns whether the type can hold signed values (false) or not (true).
Returns whether the type can hold non-integer, a.k.a. floating-point, values (false) or not (true).


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 (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*',
              defaultbadval => 'USHRT_MAX',

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 - see "$T" in PDL::PP.

  • pdlctype

    Required. The "typedef"ed 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".

  • integer

    Required. Boolean - is this an integer type?

  • unsigned

    Required. Boolean - is this an unsigned type?

  • real

    Required. Boolean - is this a real (not complex) type?

  • realversion

    String - the real version of this type (e.g. cdouble -> 'D').

  • complexversion

    String - the complex version of this type (e.g. double -> 'C').

Also have a look at the entries at the top of

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 to check for such places.

2022-10-26 perl v5.36.0