Difference between revisions of "Not"
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{{not}} | {{not}} | ||
| − | The unary operator <syntaxhighlight lang="pascal" | + | |
| − | [[FPC]] also knows the bitwise <syntaxhighlight lang="pascal" | + | The unary [[Operator|operator]] <syntaxhighlight lang="pascal" inline>not</syntaxhighlight> negates a Boolean value. |
| − | <syntaxhighlight lang="pascal" | + | [[FPC]] also knows the bitwise <syntaxhighlight lang="pascal" inline>not</syntaxhighlight> when supplied with an ordinal type. |
| + | |||
| + | <syntaxhighlight lang="pascal" inline>not</syntaxhighlight> is a [[Reserved word|reserved word]]. | ||
== Boolean operation == | == Boolean operation == | ||
| − | The operator <syntaxhighlight lang="pascal" | + | |
| + | The operator <syntaxhighlight lang="pascal" inline>not</syntaxhighlight> represents the logical negation <math>\neg A</math>. | ||
In electrical engineering one might write <math>-A</math> or <math>\overline{A}</math> instead, however the unary [[Minus|minus sign]] has a different meaning in programming. | In electrical engineering one might write <math>-A</math> or <math>\overline{A}</math> instead, however the unary [[Minus|minus sign]] has a different meaning in programming. | ||
{| class="wikitable" style="text-align:center; margin:auto;" | {| class="wikitable" style="text-align:center; margin:auto;" | ||
| − | ! <syntaxhighlight lang="pascal" | + | ! <syntaxhighlight lang="pascal" inline>A</syntaxhighlight> |
| − | ! <syntaxhighlight lang="pascal" | + | ! <syntaxhighlight lang="pascal" inline>not A</syntaxhighlight> |
|- | |- | ||
| − | | <syntaxhighlight lang="pascal" | + | | <syntaxhighlight lang="pascal" inline>false</syntaxhighlight> |
| − | | style="background: #eeeeee" | <syntaxhighlight lang="pascal" | + | | style="background: #eeeeee" | <syntaxhighlight lang="pascal" inline>true</syntaxhighlight> |
|- | |- | ||
| − | | <syntaxhighlight lang="pascal" | + | | <syntaxhighlight lang="pascal" inline>true</syntaxhighlight> |
| − | | style="background: #eeeeee" | <syntaxhighlight lang="pascal" | + | | style="background: #eeeeee" | <syntaxhighlight lang="pascal" inline>false</syntaxhighlight> |
| − | |+ | + | |+ Truth table for logical negation |
|} | |} | ||
| − | <syntaxhighlight lang="pascal" | + | <syntaxhighlight lang="pascal" inline>not</syntaxhighlight> has the highest precedence among logical operators. |
| − | == | + | == Bitwise operation == |
| − | The bitwise <syntaxhighlight lang="pascal" | + | |
| + | The bitwise <syntaxhighlight lang="pascal" inline>not</syntaxhighlight> flips every bit in an ordinal type. | ||
not 1100'1010 | not 1100'1010 | ||
――――――――――――― | ――――――――――――― | ||
0011'0101 | 0011'0101 | ||
| − | It effectively calculates the | + | It effectively calculates the one’s complement. |
| − | On virtually all platforms it is implemented by the <syntaxhighlight lang="asm" | + | On virtually all platforms it is implemented by the <syntaxhighlight lang="asm" inline>not</syntaxhighlight> instruction. |
| − | On NAND-gate-based architectures the <syntaxhighlight lang="asm" | + | On NAND-gate-based architectures the <syntaxhighlight lang="asm" inline>not</syntaxhighlight> instruction can be calculated by the expression <math>A ⌅ A</math>. |
| + | |||
| + | Note, that only <syntaxhighlight lang="pascal" inline>not %0</syntaxhighlight> will ''definitely'' result in a value interpretable as <syntaxhighlight lang="pascal" inline>true</syntaxhighlight>. | ||
| + | However, not every other <syntaxhighlight lang="pascal" inline>not x</syntaxhighlight> will result in a value interpretable as <syntaxhighlight lang="pascal" inline>false</syntaxhighlight>, since only <syntaxhighlight lang="pascal" inline>0</syntaxhighlight> is considered as <syntaxhighlight lang="pascal" inline>false</syntaxhighlight> and every other value as <syntaxhighlight lang="pascal" inline>true</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
|
not A
|
|---|---|
false
|
true
|
true
|
false
|
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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