TFPExpressionParser¶

Class for parsing and evaluating mathematical expressions

Declaration¶

Source position: fpexprpars.pp line 726

type

  TFPExpressionParser = class(TComponent)
  public
    constructor Create;
    destructor Destroy;
    function IdentifierByName : TFPExprIdentifierDef;
    procedure Clear;
    procedure EvaluateExpression;
    procedure ExtractIdentifierNames(const aExpression: AnsiString; 
                                aList: TStringList); overload;
    procedure ExtractIdentifierNames(const aExpression: AnsiString; 
                                aCallback: TIdentifierEvent); overload;
    function ExtractNode : Boolean;
    function Evaluate : TFPExpressionResult;
    function ResultType : TResultType;
    function HasAggregate : Boolean;
    procedure InitAggregate;
    procedure UpdateAggregate;
    property AsFloat: TExprFloat; {r}
    property AsCurrency: Currency; {r}
    property AsInteger: Int64; {r}
    property AsString: AnsiString; {r}
    property AsBoolean: Boolean; {r}
    property AsDateTime: TDateTime; {r}
  published
    property Expression: Ansistring; {rw}
    property Identifiers: TFPExprIdentifierDefs; {rw}
    property BuiltIns: TBuiltInCategories; {rw}
  end;

Inheritance¶

Description¶

This is the main expression parser class that provides comprehensive functionality for parsing and evaluating mathematical expressions.

The parser handles the complete expression evaluation pipeline from tokenization through parsing to evaluation, supporting complex expressions with proper operator precedence, parentheses, function calls, and variable references.

Key features include built-in mathematical functions, string operations, date/time handling, boolean logic, comparison operations, and extensibility through custom functions and variables.

Properties¶

Member	Visibility	Description
AsBoolean read only	public	Expression result as boolean value
AsCurrency read only	public	Expression result as currency value
AsDateTime read only	public	Expression result as date/time value
AsFloat read only	public	Expression result as floating point value
AsInteger read only	public	Expression result as integer value
AsString read only	public	Expression result as string value
BuiltIns	published	Manager for built-in functions and constants
Expression	published	Expression string to be evaluated
Identifiers	published	Collection of identifiers and their values

See all Properties

Methods¶

Member	Visibility	Description
Clear	public	Clear the current expression
Create	public	Create expression parser instance
Destroy	public	Destroy expression parser and free resources
Evaluate	public	Evaluate the current expression
EvaluateExpression	public	Evaluate the expression and return result
ExtractIdentifierNames	public
ExtractNode	public	Extract expression node from result
HasAggregate	public	Check if expression contains aggregates
IdentifierByName	public	Get identifier definition by name
InitAggregate	public	Initialize aggregate calculation
ResultType	public	Get the result type of the expression
UpdateAggregate	public	Update aggregate calculation with value

See all Methods