Difference between revisions of "false and true"
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{{False}} | {{False}} | ||
| − | The [[ | + | The [[Constant|constant]] <syntaxhighlight lang="pascal" enclose="none">false</syntaxhighlight> is used to define the false condition of a [[Boolean|<syntaxhighlight lang="pascal" enclose="none">boolean</syntaxhighlight>]] variable, as opposed to its opposite, [[True|<syntaxhighlight lang="pascal" enclose="none">true</syntaxhighlight>]]. |
| + | This is a [[Manifest constant|manifest constant]] which is defined as part of the [[Standard type|standard data types]] the compiler initially knows about. | ||
This constant value must be predefined by the compiler as there is no way to define it in terms of anything else. | This constant value must be predefined by the compiler as there is no way to define it in terms of anything else. | ||
| + | |||
| + | <syntaxhighlight lang="pascal"> | ||
| + | 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. | ||
| + | </syntaxhighlight> | ||
Revision as of 11:11, 2 May 2018
│
English (en) │
The constant false is used to define the false condition of a boolean variable, as opposed to its opposite, true.
This is a manifest constant which is defined as part of the standard data types the compiler initially knows about.
This constant value must be predefined by the compiler as there is no way to define it 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.
