TFPConstExpression¶

Internally used class for constant value expressions

Declaration¶

Source position: fpexprpars.pp line 472

type

  TFPConstExpression = class(TFPExprNode)
  public
    constructor CreateString;
    constructor CreateInteger;
    constructor CreateDateTime;
    constructor CreateFloat;
    constructor CreateBoolean;
    constructor CreateCurrency;
    procedure Check;
    function NodeType : TResultType;
    procedure GetNodeValue;
    function AsString : AnsiString;
    property ConstValue: TFPExpressionResult; {r}
  end;

Inheritance¶

Description¶

The TFPConstExpression class represents constant literal values in expressions, storing fixed values that do not change during expression evaluation. It provides the foundation for all literal constants including strings, integers, floats, booleans, and date/time values.

Constant expressions are the leaf nodes of expression trees that provide actual data values rather than computed results. They are essential building blocks that supply the raw data that other expression nodes operate on.

The class handles various data types through different constructor methods and provides type-safe storage and retrieval of constant values during expression evaluation.

This class is used internally by the TFPExpressionParser class to construct an AST (Abstract Syntax Tree). There is normally no need for you to use or instantiate this class directly.

Properties¶

Member	Visibility	Description
ConstValue read only	public	The constant value stored in the expression

See all Properties

Methods¶

Member	Visibility	Description
AsString	public	Get string representation of constant expression
Check	public	Validate the constant expression
CreateBoolean	public	Create constant expression with boolean value
CreateCurrency	public	Create constant expression with currency value
CreateDateTime	public	Create constant expression with datetime value
CreateFloat	public	Create constant expression with float value
CreateInteger	public	Create constant expression with integer value
CreateString	public	Create constant expression with string value
GetNodeValue	public	Get the constant value
NodeType	public	Get the result type for constant expressions

See all Methods