Difference between revisions of "Type"
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The [[Reserved word|reserved word]] <syntaxhighlight lang="pascal" enclose="none">type</syntaxhighlight> is used to: | The [[Reserved word|reserved word]] <syntaxhighlight lang="pascal" enclose="none">type</syntaxhighlight> is used to: | ||
* start sections for user defined types, and | * start sections for user defined types, and | ||
| − | * identify a new type instance when referring to another data type. | + | * identify a new type instance when referring to another [[Data type|data type]]. |
| − | |||
== custom type definitions == | == custom type definitions == | ||
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== type aliases == | == type aliases == | ||
| − | In a <syntaxhighlight lang="pascal" enclose="none">type</syntaxhighlight> section aliases to already | + | In a <syntaxhighlight lang="pascal" enclose="none">type</syntaxhighlight> section aliases to already existing or previously defined data types can be declared. |
The following example utilizes [[Conditional compilation|conditional compilation]] to alias the largest available unsigned integer type as <syntaxhighlight lang="pascal" enclose="none">wholeNumber</syntaxhighlight> (note there is already {{Doc|package=RTL|unit=system|identifier=sizeuint|text=<syntaxhighlight lang="pascal" enclose="none">system.sizeUInt</syntaxhighlight>}} defined). | The following example utilizes [[Conditional compilation|conditional compilation]] to alias the largest available unsigned integer type as <syntaxhighlight lang="pascal" enclose="none">wholeNumber</syntaxhighlight> (note there is already {{Doc|package=RTL|unit=system|identifier=sizeuint|text=<syntaxhighlight lang="pascal" enclose="none">system.sizeUInt</syntaxhighlight>}} defined). | ||
<syntaxhighlight lang="pascal" line highlight="3"> | <syntaxhighlight lang="pascal" line highlight="3"> | ||
Revision as of 00:04, 2 June 2018
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The reserved word type is used to:
- start sections for user defined types, and
- identify a new type instance when referring to another data type.
custom type definitions
type starts a section, where the programmer may associate identifiers with new data types, especially structured data types such as records.
1program typeDemo(input, output, stderr);
2
3type
4 atom = record
5 electrons: longword;
6 neutrons: longword;
7 protons: longword;
8 end;
9
10var
11 x: atom;
12
13begin
14 x.protons := 1; // H
15 x.neutrons := 1; // D
16 x.electrons := 1; // 0
17end.
type aliases
In a type section aliases to already existing or previously defined data types can be declared.
The following example utilizes conditional compilation to alias the largest available unsigned integer type as wholeNumber (note there is already system.sizeUInt defined).
1program typeAliasDemo(input, output, stderr);
2
3type
4 wholeNumber =
5 {$ifdef CPU64}
6 qword
7 {$else}
8 {$ifdef CPU32}
9 longword
10 {$else}
11 {$fatal natural number too small}
12 {$endif}
13 {$endif}
14 ;
15
16begin
17end.
type clone
In a type section a type identifier preceded by the word type actually clones the type, with its type information, but creating different types.
1program typeCloneDemo(input, output, stderr);
2
3type
4 wholeNumber = type qword;
5
6begin
7 writeLn('qword: ', sysBackTraceStr(typeInfo(qword)));
8 writeLn('wholeNumber: ', sysBackTraceStr(typeInfo(wholeNumber)));
9end.
