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Microsoft Visual Basic for Applications Language Reference

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Microsoft Visual Basic for

Applications Language Reference

– Operator

Description

Used to find the difference between two numbers or to indicate the negative value of a numeric

expression.

Syntax 1

result = number1–number2

Syntax 2

–number

The – operator syntax has these parts

Part

Description

result

Required; any numeric variable.

number Required; any numeric expression.

number1 Required; any numeric expression.

number2 Required; any numeric expression.

Remarks

In Syntax 1, the – operator is the arithmetic subtraction operator used to find the difference

between two numbers. In Syntax 2, the – operator is used as the unary negation operator to

indicate the negative value of an expression.

The data type of result is usually the same as that of the most precise expression. The order of

precision, from least to most precise, is Byte, Integer, Long, Single, Double, Currency, and

Decimal. The following are exceptions to this order

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Then result is

Subtraction involves a

Single and a Long,

converted to a Double.

The data type of result is a

Long, Single, or Date

variant that overflows its

legal range,

converted to a Variant

containing a Double.

The data type of result is a

Byte variant that overflows

its legal range,

converted to an Integer

variant.

The data type of result is

an Integer variant that

overflows its legal range,

converted to a Long

variant.

Subtraction involves a Date

and any other data type,

a Date.

Subtraction involves two

Date expressions,

a Double.

One or both expressions are Null expressions, result is Null. If an expression is Empty, it is

treated as 0.

Note The order of precision used by addition and subtraction is not the same as the order of

precision used by multiplication.

See Also

Operator precedence.

Example

This example uses the – operator to calculate the difference between two numbers.

Dim MyResult

MyResult=4-2

' Returns 124.45.

#Const Directive

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MyResult = 459.35 - 334.90

'Returns 2.

Microsoft Visual Basic for Applications Language Reference

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Description

Used to define conditional compiler constants for Visual Basic.

Syntax

#Const constname = expression

The #Const compiler directive syntax has these parts

Part

Description

constname Required; Variant (String). Name of the

constant; follows standard variable naming

conventions.

expression Required. Literal, other conditional

compiler constant, or any combination that

includes any or all arithmetic or logical

operators except Is.

Remarks

Conditional compiler constants are always Private to the module in which they appear. It is not

possible to create Public compiler constants using the #Const directive. Public compiler

constants can only be created in the user interface.

Only conditional compiler constants and literals can be used in expression. Using a standard

constant defined with Const, or using a constant that is undefined, causes an error to occur.

Conversely, constants defined using the #Const keyword can only be used for conditional

compilation.

Conditional compiler constants are always evaluated at the module level, regardless of their

placement in code.

See Also

#If...Then...# Else directive, Const statement.

Specifics (Microsoft Access)

In Microsoft Access, you can define a public conditional compiler constant in the Declarations

section of a module. A public compiler constant is applicable to all modules in the current

database, but not in any other database.

You can also declare a public compiler constant by clicking Options on the Tools menu, then

clicking the Advanced tab. Enter the constant in the Conditional Compilation Arguments box.

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For example, you might enter the following expression into the Conditional Compilation

Arguments box.

conDebug = 1

You can use a public compiler constant in code in any module. For example, you can create an

#If...Then...#Else construct to optionally run debug code.

#If conDebug = 1 Then

' Run debug code.

#Else

#End If

' Run streamlined code.

To create multiple public conditional compilation constants, declare them on separate lines in

the Declaration section. In the Conditional Compilation Arguments box, separate them with

colons. For example, you can enter the following conditional compilation constants in the

Conditional Compilation Arguments box.

conActiveLanguage=1:conDebug = 1

You can use a logical operator to include both constants in an #If...Then...#Else construct. In

the following example, the first segment of code runs only if both constants are currently equal

to 1, so that the expression containing the constants is true.

#If (conActiveLanguage = 1 And conDebug = 1) Then

' Run debug code for the active language version.

#Else

#End If

' Run another code segment.

If either or both constants have a different value, then the code in the #Else portion of the

construct runs. To change which block of code runs, you can simply change the values of the

constants.

Notes

A conditional compilation constant is always evaluated with a text-based string

comparison method. This evaluation is equivalent to having an Option Compare Text

statement in the module and occurs even if the module contains an Option Compare

Database statement.

When writing code for conditional compilation, it may be less confusing to view one

procedure at a time rather than all procedures in the module. To change how you view

your code, click Options on the Tools menu, then click the Module tab. Under Code View,

clear the Full Module View check box.

Example

This example uses the #Const directive to declare conditional compiler constants for use in

#If...#Else...#End If constructs.

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#Const DebugVersion = 1

' Will evaluate true in #If block.

#If...Then...#Else Directive

Description

Conditionally compiles selected blocks of Visual Basic code.

Syntax

#If expression Then

statements

[#ElseIf expression-n Then

[elseifstatements]]

[#Else

[elsestatements]]

#End If

The #If...Then...#Else directive syntax has these parts

Part

Description

expression

Required. Any expression, consisting

exclusively of one or more conditional

compiler constants, literals, and

operators, that evaluates to True or

False.

statements

Required. Visual Basic program lines or

compiler directives that are evaluated if

the associated expression is True.

expression-n

Optional. Any expression, consisting

exclusively of one or more conditional

compiler constants, literals, and

operators, that evaluates to True or

False.

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