Difference between revisions of "false and true"
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| − | The [[Constant| | + | The [[Constant|constants]] <syntaxhighlight lang="pascal" enclose="none">false</syntaxhighlight> and <syntaxhighlight lang="pascal" enclose="none">true</syntaxhighlight> are used to define the false and true conditions of a [[Boolean|<syntaxhighlight lang="pascal" enclose="none">boolean</syntaxhighlight>]] [[Variable|variable]]. |
| − | + | They are [[Manifest constant|manifest constants]] that are defined as part of the [[Standard type|standard data types]] the [[Compiler|compiler]] initially knows about. | |
| − | This constant | + | This constant values must be predefined by the compiler as there is no way to define them in terms of anything else. |
<syntaxhighlight lang="pascal"> | <syntaxhighlight lang="pascal"> | ||
Revision as of 12:43, 4 May 2018
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English (en) │
The constants false and true are used to define the false and true conditions of a boolean variable.
They are manifest constants that are defined as part of the standard data types the compiler initially knows about.
This constant values must be predefined by the compiler as there is no way to define them in terms of anything else.
program falseDemo(input, output, stderr);
uses
typInfo;
begin
writeLn(false); // prints FALSE
// enumerative actions ------------------------------------------
writeLn(ord(false)); // prints 0
writeLn(succ(false)); // prints TRUE
// next two statements generate out-of-range compile-time warnings
writeLn(pred(false)); // prints TRUE
writeLn(succ(succ(false))); // prints TRUE
// data type ----------------------------------------------------
writeLn(sizeOf(false)); // prints 1
writeLn(bitSizeOf(false)); // prints 8
writeLn(PTypeInfo(typeInfo(false))^.kind); // prints tkBool
writeLn(PTypeInfo(typeInfo(false))^.name); // prints Boolean
end.
