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 $pdl->type->realctype() . "'\n";
14 The actual c type used to store ushort's is 'unsigned short'
15
17 Internal module - holds all the PDL Type info. The type info can be
18 accessed easily using the "PDL::Type" object returned by the type
19 method.
20 Skip to the end of this document to find out how to change the set of
22 types supported by PDL.
23
25 A number of functions are available for module writers to get/process
26 type information. These are used in various places (e.g. "PDL::PP",
27 "PDL::Core") to generate the appropriate type loops, etc.
28 typesrtkeys
30 return array of keys of typehash sorted in order of type complexity
32 ppdefs
34 return array of pp symbols for all known types
36 typefld
38 return specified field ($fld) for specified type ($type) by querying
40 type hash
41 mapfld
43 map a given source field to the corresponding target field by querying
45 the type hash
46 typesynonyms
48 return type related synonym definitions to be included in pdl.h . This
50 routine must be updated to include new types as required. Mostly the
51 automatic updating should take care of the vital things.
52
54 This module declares one class - "PDL::Type" - objects of this class
55 are returned by the type method of a piddle. It has several methods,
56 listed below, which provide an easy way to access type information:
57 Additionally, comparison and stringification are overloaded so that you
59 can compare and print type objects, e.g.
60 $nofloat = 1 if $pdl->type < float;
62 die "must be double" if $type != double;
63 For further examples check again the type method.
65 enum
67 Returns the number representing this datatype (see get_datatype).
68 symbol
70 Returns one of 'PDL_B', 'PDL_S', 'PDL_US', 'PDL_L', 'PDL_LL',
71 'PDL_F' or 'PDL_D'.
72 ctype
74 Returns the macro used to represent this type in C code (eg
75 'PDL_Long').
76 ppsym
78 The letter used to represent this type in PP code code (eg 'U' for
79 ushort).
80 realctype
82 The actual C type used to store this type.
83 shortctype
85 The value returned by "ctype" without the 'PDL_' prefix.
86 badvalue
88 Since PDL was compiled without support for 'bad' values, this rou‐
89 tine returns undef.
90 orig_badvalue
92 Since PDL was compiled without support for 'bad' values, this rou‐
93 tine returns undef.
94
96 You can change the types that PDL knows about by editing entries in the
97 definition of the variable @types that appears close to the top of the
98 file Types.pm.PL (i.e. the file from which this module was generated).
99 Format of a type entry
101 Each entry in the @types array is a hash reference. Here is an example
103 taken from the actual code that defines the "ushort" type:
104 {
106 identifier => 'US',
107 onecharident => 'U', # only needed if different from identifier
108 pdlctype => 'PDL_Ushort',
109 realctype => 'unsigned short',
110 ppforcetype => 'ushort',
111 usenan => 0,
112 packtype => 'S*',
113 },
114 Before we start to explain the fields please take this important mes‐
116 sage on board: entries must be listed in order of increasing complex‐
117 ity. This is critical to ensure that PDL"s type conversion works cor‐
118 rectly. Basically, a less complex type will be converted to a more
119 complex type as required.
120 Fields in a type entry
122 Each type entry has a number of required and optional entry.
124 A list of all the entries:
126 · identifier
128 Required. A short sequence of upercase letters that identifies this
130 type uniquely. More than three characters is probably overkill.
131 · onecharident
133 Optional. Only required if the "identifier" has more than one char‐
135 acter. This should be a unique uppercase character that will be
136 used to reference this type in PP macro expressions of the
137 "TBSULFD" type. If you don't know what I am talking about read the
138 PP manpage or ask on the mailing list.
139 · pdlctype
141 Required. The "typedefed" name that will be used to access this
143 type from C code.
144 · realctype
146 Required. The C compiler type that is used to implement this type.
148 For portability reasons this one might be platform dependent.
149 · ppforcetype
151 Required. The type name used in PP signatures to refer to this
153 type.
154 · usenan
156 Required. Flag that signals if this type has to deal with NaN
158 issues. Generally only required for floating point types.
159 · packtype
161 Required. The Perl pack type used to pack Perl values into the
163 machine representation for this type. For details see "perldoc -f
164 pack".
165 Also have a look at the entries at the top of Types.pm.PL.
167 The syntax is not written into stone yet and might change as the con‐
169 cept matures.
170 Other things you need to do
172 You need to check modules that do I/O (generally in the IO part of the
174 directory tree). In the future we might add fields to type entries to
175 automate this. This requires changes to those IO modules first though.
176 You should also make sure that any type macros in PP files (i.e.
178 "$TBSULFD...") are updated to reflect the new type. PDL::PP::Dump has a
179 mode to check for type macros requiring updating. Do something like
180 find . -name \*.pd -exec perl -Mblib=. -M'PDL::PP::Dump=typecheck' {} \;
182 from the PDL root directory after updating Types.pm.PL to check for
184 such places.
185perl v5.8.8 2002-05-21 Types(3)