Boolean Data Type

Purpose

The Boolean type represents the two logical values, True and False.

Syntax

Dim name As Boolean | Bool

Dim Name?

Description

Type declaration character is ?. Range: -1 - 0.

False = 0

True = -1

Boolean values are stored in a Byte.

With an array of Bool the values are stored in a bit.

When other numeric types are converted to Boolean values, 0 becomes False and all other values become True. When Boolean values are converted to other data types, False becomes 0, and True becomes -1.

Example

Dim d As Boolean = -1

Local Bool d1 = True

Global d2?

Dim f?(7)   // occupies 1 Byte

Dim f2?(10) // occupies 2 bytes

Known Issues

1. Note There is a compiler bug when setting the eighth Bool in a row of 8 Booleans to False. The entire byte containing the 8 Booleans is affected, because setting the eighth bit generates an 'and a-byte, 8' assembler instruction.

   Type BoolTrouble

   a0 As Bool

   a1 As Bool

   a2 As Bool

   a3 As Bool

   a4 As Bool

   a5 As Bool

   a6 As Bool

   a7 As Bool' <- 8th bool in a row

   EndType

   Dim bl As BoolTrouble

   Message bl.a0

   bl.a0 = True

   Message bl.a0

   bl.a7 = False  ' and V:bl.a0, 8

   Message bl.a0

   You have a few options. You could use the eighth bit as a dummy and don't use it. Or, you can explicitly set and clear the bit:

   Bset bl.a7, 1' bl.a7 = True

   Bclr bl.a7, 1' bl.a7 = False

   
   
2. Occasionally, setting a boolean using a complex statement will cause an odd result, as the next time it is called it is not recognised (if it is TRUE).

   Local alignadj? = ((wb.align And 3) = 3)

   If alignadj? Then Sub wb.align, 3 // If true, this line is ignored

   If alignadj? Then Add wb.align, 2 // This line is actioned

   The workaround is to change line one to:

   Local alignadj? : If ((wb.Align And 3) = 3) Then alignadj? = True

   [Reported by James Gaite, 27/05/2020]

See Also

Boolean, Byte, Card, Short, Word, Int16, Long, Int, Integer, Int32, Int64, Large, Single, Double, Currency, Date, Handle, String, Variant, Object

{Created by Sjouke Hamstra; Last updated: 29/06/2020 by James Gaite}