Modern Math NegChecked

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NegChecked

Negates an integer, returning an empty Optional for the most negative value.

Syntax

NegChecked( byval a as T ) as Optional( of T )

Notes

• One failing case, and it is the same one AbsChecked has: the most negative value of a two's-complement type has no positive counterpart. On a BYTE there is no +128.
• Every other input negates cleanly.
• NegSaturating clamps that case and NegWrapping returns it unchanged, which is what the bare - already does.

Examples

#import "std/numeric"
using numeric

dim as int8 worst = -128

var r = NegChecked( worst )
print r.HasValue( )          '' false -- there is no +128 in a BYTE

'' The bare operator does something DIFFERENT again: it promotes the
'' BYTE to an integer first, so the answer is a correct 128 that no
'' longer fits back in the type it came from
print -worst                 '' 128

dim as int8 ordinary = 100
print NegChecked( ordinary ).Value( )         '' -100

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Library: Math Library
Category: Math Library
Documented under: Members