Difference between revisions of "Not"
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For example, <syntaxhighlight lang="delphi" inline>boolean(not %1)</syntaxhighlight> will evaluate as <syntaxhighlight lang="pascal" inline>true</syntaxhighlight>, but only <syntaxhighlight lang="delphi" inline>boolean(not high(nativeUInt))</syntaxhighlight> will evaluate to <syntaxhighlight lang="pascal" inline>false</syntaxhighlight>. | For example, <syntaxhighlight lang="delphi" inline>boolean(not %1)</syntaxhighlight> will evaluate as <syntaxhighlight lang="pascal" inline>true</syntaxhighlight>, but only <syntaxhighlight lang="delphi" inline>boolean(not high(nativeUInt))</syntaxhighlight> will evaluate to <syntaxhighlight lang="pascal" inline>false</syntaxhighlight>. | ||
| − | == | + | {{Logical operators}} |
| + | * {{Doc|package=RTL|unit=system|identifier=.op-logicalnot-variant-ariant|text=<syntaxhighlight lang="pascal" inline>system.logicalNot</syntaxhighlight>}} | ||
| − | + | [[Category:Operators]] | |
Latest revision as of 23:14, 16 October 2020
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The unary operator not negates a Boolean value.
FPC also knows the bitwise not when supplied with an ordinal type.
not is a reserved word.
Boolean operation
The operator not represents the logical negation [math]\displaystyle{ \neg A }[/math].
In electrical engineering one might write [math]\displaystyle{ -A }[/math] or [math]\displaystyle{ \overline{A} }[/math] instead, however the unary minus sign has a different meaning in programming.
A
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not A
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false
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true
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true
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false
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not has the highest precedence among logical operators.
Bitwise operation
The bitwise not flips every bit in an ordinal type.
not 1100'1010
―――――――――――――
0011'0101
It effectively calculates the one’s complement.
On virtually all platforms it is implemented by the not instruction.
On NAND-gate-based architectures the not instruction can be calculated by the expression [math]\displaystyle{ A ⌅ A }[/math].
Note, that only not %0 will definitely result in a value interpretable as true.
However, not every other not x will result in a value interpretable as false, since only 0 is considered as false and every other value as true.
For example, boolean(not %1) will evaluate as true, but only boolean(not high(nativeUInt)) will evaluate to false.
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