1Types(3) User Contributed Perl Documentation Types(3)
2
6 PDL::Types - define fundamental PDL Datatypes
7
9 use PDL::Types;
10 $pdl = ushort( 2.0, 3.0 );
12 print "The actual c type used to store ushort's is '" .
13 $pdl->type->realctype() . "'\n";
14 The actual c type used to store ushort's is 'unsigned short'
15
17 Internal module - holds all the PDL Type info. The type info can be
18 accessed easily using the "PDL::Type" object returned by the type
19 method.
20 Skip to the end of this document to find out how to change the set of
22 types supported by PDL.
23
25 A number of functions are available for module writers to get/process
26 type information. These are used in various places (e.g. "PDL::PP",
27 "PDL::Core") to generate the appropriate type loops, etc.
28 typesrtkeys
30 return array of keys of typehash sorted in order of type complexity
31 ppdefs
33 return array of pp symbols for all known types
34 typefld
36 return specified field ($fld) for specified type ($type) by querying
37 type hash
38 mapfld (in_value, in_key, out_key)
40 Map a given source field to the corresponding target field by querying
41 the type hash. This gives you a way to say, "Find the type whose
42 $in_key is equal to $value, and return that type's value for $out_key.
43 For example:
44 # Does byte type use nan?
46 $uses_nan = PDL::Types::mapfld(byte => 'ppforcetype', 'usenan');
47 # Equivalent:
48 $uses_nan = byte->usenan;
49 # What is the actual C type for the value that we call 'long'?
51 $type_name = PDL::Types::mapfld(long => 'convertfunc', 'realctype');
52 # Equivalent:
53 $type_name = long->realctype;
54 As you can see, the equivalent examples are much shorter and legible,
56 so you should only use mapfld if you were given the type index (in
57 which case the actual type is not immediately obvious):
58 $type_index = 4;
60 $type_name = PDL::Types::mapfld($type_index => numval, 'realctype');
61 typesynonyms
63 return type related synonym definitions to be included in pdl.h . This
64 routine must be updated to include new types as required. Mostly the
65 automatic updating should take care of the vital things.
66 datatypes_header
68 return C header text for pdl.h and pdlsimple.h.
69
71 This module declares one class - "PDL::Type" - objects of this class
72 are returned by the type method of a piddle. It has several methods,
73 listed below, which provide an easy way to access type information:
74 Additionally, comparison and stringification are overloaded so that you
76 can compare and print type objects, e.g.
77 $nofloat = 1 if $pdl->type < float;
79 die "must be double" if $type != double;
80 For further examples check again the type method.
82 enum
84 Returns the number representing this datatype (see get_datatype).
85 symbol
87 Returns one of 'PDL_B', 'PDL_S', 'PDL_US', 'PDL_L', 'PDL_IND',
88 'PDL_LL', 'PDL_F' or 'PDL_D'.
89 ctype
91 Returns the macro used to represent this type in C code (eg
92 'PDL_Long').
93 ppsym
95 The letter used to represent this type in PP code code (eg 'U' for
96 ushort).
97 realctype
99 The actual C type used to store this type.
100 shortctype
102 The value returned by "ctype" without the 'PDL_' prefix.
103 badvalue
105 The special numerical value used to represent bad values for this
106 type. See badvalue routine in PDL::Bad for more details.
107 orig_badvalue
109 The default special numerical value used to represent bad values
110 for this type. (You can change the value that represents bad values
111 for each type during runtime.) See the orig_badvalue routine in
112 PDL::Bad for more details.
113
115 You can change the types that PDL knows about by editing entries in the
116 definition of the variable @types that appears close to the top of the
117 file Types.pm.PL (i.e. the file from which this module was generated).
118 Format of a type entry
120 Each entry in the @types array is a hash reference. Here is an example
121 taken from the actual code that defines the "ushort" type:
122 {
124 identifier => 'US',
125 onecharident => 'U', # only needed if different from identifier
126 pdlctype => 'PDL_Ushort',
127 realctype => 'unsigned short',
128 ppforcetype => 'ushort',
129 usenan => 0,
130 packtype => 'S*',
131 },
132 Before we start to explain the fields please take this important
134 message on board: entries must be listed in order of increasing
135 complexity. This is critical to ensure that PDL's type conversion works
136 correctly. Basically, a less complex type will be converted to a more
137 complex type as required.
138 Fields in a type entry
140 Each type entry has a number of required and optional entry.
141 A list of all the entries:
143 · identifier
145 Required. A short sequence of upercase letters that identifies this
147 type uniquely. More than three characters is probably overkill.
148 · onecharident
150 Optional. Only required if the "identifier" has more than one
152 character. This should be a unique uppercase character that will
153 be used to reference this type in PP macro expressions of the
154 "TBSULFD" type. If you don't know what I am talking about read the
155 PP manpage or ask on the mailing list.
156 · pdlctype
158 Required. The "typedefed" name that will be used to access this
160 type from C code.
161 · realctype
163 Required. The C compiler type that is used to implement this type.
165 For portability reasons this one might be platform dependent.
166 · ppforcetype
168 Required. The type name used in PP signatures to refer to this
170 type.
171 · usenan
173 Required. Flag that signals if this type has to deal with NaN
175 issues. Generally only required for floating point types.
176 · packtype
178 Required. The Perl pack type used to pack Perl values into the
180 machine representation for this type. For details see "perldoc -f
181 pack".
182 Also have a look at the entries at the top of Types.pm.PL.
184 The syntax is not written into stone yet and might change as the
186 concept matures.
187 Other things you need to do
189 You need to check modules that do I/O (generally in the IO part of the
190 directory tree). In the future we might add fields to type entries to
191 automate this. This requires changes to those IO modules first though.
192 You should also make sure that any type macros in PP files (i.e.
194 "$TBSULFD...") are updated to reflect the new type. PDL::PP::Dump has a
195 mode to check for type macros requiring updating. Do something like
196 find . -name \*.pd -exec perl -Mblib=. -M'PDL::PP::Dump=typecheck' {} \;
198 from the PDL root directory after updating Types.pm.PL to check for
200 such places.
201perl v5.30.0 2019-09-05 Types(3)