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Constants (Delphi and Access VBA Cross Reference Guide)

By Mike Prestwood

Delphi versus Access VBA: A side by side comparison between Delphi and Access VBA.

 
Language Basics
 

Language basics is kind of a catch all for absolute beginner stuff. The items (common names) I chose for language basics is a bit random and include items like case sensitivity, commenting, declaring variables, etc.

Constants

[Other Languages] 

General Info: Computer Language Constants

A constant is just like a variable (it holds a value) but, unlike a variable, you cannot change the value of a constant.

Delphi:   Const kPI: Double=3.1459;

In Delphi, you define constants similar to how you define variables but use the Const keyword instead of the Var keyword. Declare global constants in a unit's interface section and unit constants (scope limited to unit) in the implementation section. Declare local constants above the begin..end block.

Syntax Example:
Const 
  kFeetToMeter: Double = 3.2808;
  kMeterToFeet: Double = .3048;
  kName: String = "Mike";
 
//Local constants:
procedure SomeProcedure;
const
  kPI: Double=3.1459;
begin
end;
Access VBA:   Const kPI = 3.1459

Scope can be Public, Global, or Private. The use of the newer Public keyword is preferred to the older Global. Private Const is the same as just specifying Const.

Syntax Example:
Const kPI = 3.1459
Const kName = "Mike"
 
//Public variable:
Public Const kFeetToMeter=3.28, kMeterToFeet=.3













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