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 $pdl->type->realctype() . "'\n";
14 The actual c type used to store ushort's is 'unsigned short'
15
17 Internal module - holds all the PDL Type info. The type info can be
18 accessed easily using the "PDL::Type" object returned by the type
19 method.
20 Skip to the end of this document to find out how to change the set of
22 types supported by PDL.
23
25 A number of functions are available for module writers to get/process
26 type information. These are used in various places (e.g. "PDL::PP",
27 "PDL::Core") to generate the appropriate type loops, etc.
28 typesrtkeys
30 Returns an array of keys of typehash sorted in order of type complexity
31 pdl> @typelist = PDL::Types::typesrtkeys;
33 pdl> print @typelist;
34 PDL_B PDL_S PDL_US PDL_L PDL_IND PDL_LL PDL_F PDL_D
35 ppdefs
37 Returns an array of pp symbols for all known types
38 pdl> @ppdefs = PDL::Types::ppdefs
40 pdl> print @ppdefs;
41 B S U L N Q F D
42 typefld
44 Returns specified field ($fld) for specified type ($type) by querying
45 type hash
46 PDL::Types::typefld($type,$fld);
48 pdl> print PDL::Types::typefld('PDL_IND',realctype)
50 long
51 mapfld
53 Map a given source field to the corresponding target field by querying
54 the type hash. This gives you a way to say, "Find the type whose
55 $in_key is equal to $value, and return that type's value for $out_key.
56 For example:
57 # Does byte type use nan?
59 $uses_nan = PDL::Types::mapfld(byte => 'ppforcetype', 'usenan');
60 # Equivalent:
61 $uses_nan = byte->usenan;
62 # What is the actual C type for the value that we call 'long'?
64 $type_name = PDL::Types::mapfld(long => 'convertfunc', 'realctype');
65 # Equivalent:
66 $type_name = long->realctype;
67 As you can see, the equivalent examples are much shorter and legible,
69 so you should only use mapfld if you were given the type index (in
70 which case the actual type is not immediately obvious):
71 $type_index = 4;
73 $type_name = PDL::Types::mapfld($type_index => numval, 'realctype');
74 typesynonyms
76 return type related synonym definitions to be included in pdl.h . This
77 routine must be updated to include new types as required. Mostly the
78 automatic updating should take care of the vital things.
79 datatypes_header
81 return C header text for pdl.h and pdlsimple.h.
82
84 This module declares one class - "PDL::Type" - objects of this class
85 are returned by the type method of a piddle. It has several methods,
86 listed below, which provide an easy way to access type information:
87 Additionally, comparison and stringification are overloaded so that you
89 can compare and print type objects, e.g.
90 $nofloat = 1 if $pdl->type < float;
92 die "must be double" if $type != double;
93 For further examples check again the type method.
95 enum
97 Returns the number representing this datatype (see get_datatype).
98 symbol
100 Returns one of 'PDL_B', 'PDL_S', 'PDL_US', 'PDL_L', 'PDL_IND',
101 'PDL_LL', 'PDL_F' or 'PDL_D'.
102 ctype
104 Returns the macro used to represent this type in C code (eg
105 'PDL_Long').
106 ppsym
108 The letter used to represent this type in PP code code (eg 'U' for
109 ushort).
110 realctype
112 The actual C type used to store this type.
113 shortctype
115 The value returned by "ctype" without the 'PDL_' prefix.
116 badvalue
118 The special numerical value used to represent bad values for this
119 type. See badvalue routine in PDL::Bad for more details.
120 orig_badvalue
122 The default special numerical value used to represent bad values
123 for this type. (You can change the value that represents bad values
124 for each type during runtime.) See the orig_badvalue routine in
125 PDL::Bad for more details.
126
128 You can change the types that PDL knows about by editing entries in the
129 definition of the variable @types that appears close to the top of the
130 file Types.pm.PL (i.e. the file from which this module was generated).
131 Format of a type entry
133 Each entry in the @types array is a hash reference. Here is an example
134 taken from the actual code that defines the "ushort" type:
135 {
137 identifier => 'US',
138 onecharident => 'U', # only needed if different from identifier
139 pdlctype => 'PDL_Ushort',
140 realctype => 'unsigned short',
141 ppforcetype => 'ushort',
142 usenan => 0,
143 packtype => 'S*',
144 },
145 Before we start to explain the fields please take this important
147 message on board: entries must be listed in order of increasing
148 complexity. This is critical to ensure that PDL's type conversion works
149 correctly. Basically, a less complex type will be converted to a more
150 complex type as required.
151 Fields in a type entry
153 Each type entry has a number of required and optional entry.
154 A list of all the entries:
156 · identifier
158 Required. A short sequence of upercase letters that identifies this
160 type uniquely. More than three characters is probably overkill.
161 · onecharident
163 Optional. Only required if the "identifier" has more than one
165 character. This should be a unique uppercase character that will
166 be used to reference this type in PP macro expressions of the
167 "TBSULFD" type. If you don't know what I am talking about read the
168 PP manpage or ask on the mailing list.
169 · pdlctype
171 Required. The "typedefed" name that will be used to access this
173 type from C code.
174 · realctype
176 Required. The C compiler type that is used to implement this type.
178 For portability reasons this one might be platform dependent.
179 · ppforcetype
181 Required. The type name used in PP signatures to refer to this
183 type.
184 · usenan
186 Required. Flag that signals if this type has to deal with NaN
188 issues. Generally only required for floating point types.
189 · packtype
191 Required. The Perl pack type used to pack Perl values into the
193 machine representation for this type. For details see "perldoc -f
194 pack".
195 Also have a look at the entries at the top of Types.pm.PL.
197 The syntax is not written into stone yet and might change as the
199 concept matures.
200 Other things you need to do
202 You need to check modules that do I/O (generally in the IO part of the
203 directory tree). In the future we might add fields to type entries to
204 automate this. This requires changes to those IO modules first though.
205 You should also make sure that any type macros in PP files (i.e.
207 "$TBSULFD...") are updated to reflect the new type. PDL::PP::Dump has a
208 mode to check for type macros requiring updating. Do something like
209 find . -name \*.pd -exec perl -Mblib=. -M'PDL::PP::Dump=typecheck' {} \;
211 from the PDL root directory after updating Types.pm.PL to check for
213 such places.
214perl v5.30.2 2020-04-02 Types(3)