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Constants (Delphi and Corel Paradox Cross Reference Guide)

By Mike Prestwood

Delphi versus Corel Paradox: A side by side comparison between Delphi and Corel Paradox.

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;

Delphi Constants (Const kPI: Double=3.1459;) 1 certification question.

Corel Paradox: const..endConst

In ObjectPAL, you declare one or more constant values within a const..endConst block. Optionally, you can specify the dataType by casting the value as part of the declaration.

If you do not specify the data type, the data type is inferred from the value as either a LongInt, a Number, a SmallInt, or a String.

As with variables, the const..endConst block can come within a method or procedure as the first bit of code, or in the Const window. Putting it above the method or procedure is allowed but has no significance so don't.

Syntax Example:

const
  kFeetToMeter = Number(3.2808)
  kMeterToFeet = Number(.3048)
  kName = String("Mike")

  kCA = "California"     ;String inferred.
endConst

ObjectPAL Constants (const..endConst) 1 certification question.