Ry Formula Evaluator

Mathematical formula compiler&evaluator - VCL Component for Delphi.

TRyFormulaEval is a native Delphi component designed to evaluate mathematical formulas. Performace of this evaluation is improved by compiling the formula to assembler code, internally. TRyFormulaEval implements parse once-evaluate many times type of parsing for mathematical expressions given as strings. It allows creation of custom variables and functions to be used in the expressions; once defined, functions can be redefined in runtime and extremely fast, resulting a very powerful tool.
Its internal arithmetic uses ‘Extended’ storage for floating point numbers.
Variable values can be set in three different ways: OnFindVariable event oriented, reference by name, reference by index. Thread safe.

Features

Standard mathemathical operators and delimiters: + - * / ^ ( ) , . ;
Supports standard functions: ABS, COS, LOG10, LN, MAX, MIN, PERCENT, PORCENTAJE, SIN, TAN
Standard functions can be deactivated on demand. (Better performance in applications that does not require std functions)
Supports external user defined functions.
Standard or user defined functions can have multiple names, pointing to the same function.
Runtime overload of functions. Standard or user defined functions can be redeclared, pointing to another function implementation.
Supports unlimmited number of parenthesis nesting.
Supports unlimited number of variables.
All operations are compiled to a buffer containing assembly code. An evaluation consists of a single "jump" to this memory buffer, so no bifurcation takes places at evaluation time (excellent performance).
Thread safe.
No internal tree structure, each character of the string that defines the formula is read just once (parsing time is reduced).
Three methods are provided to access variables, event oriented, reference by name and reference by index.

Unsupported features

RyFormulaEval is an optimized numerical mathematical formula evaluator, so these features are not supported:

Strings
Boolean
Conditionals

Installation

No installation needed. Just include RyFormulaEval.pas (or dcu) in your project and add it to the uses clause/s.

Properties, Methods and Events

Types
PVariable = ^TVariable;
TVariable = record
Value: Extended;
end;
TExprMathFunction = function(var values: array of Extended): Extended of object;
TExprMathOnFindVariable = procedure(VariableName: string; var Value: Extended) of object;

Properties
    Formula: string
    Result: Extended
    VarCount: Integer
    VarByName[VariableName: string]: PVariable
    VarByIndex[Idx: Integer]: PVariable

Methods
    function GetVarIndex(VariableName: string): Integer;
    function AddFunctionDecl(FunctionName: string; NumParams: Integer;
CustomFunction: TExprMathFunction): Boolean;
    function ModifyFunctionDecl(FunctionName: string; CustomFunction: TExprMathFunction): Integer;
    function ResultNOCompile: Extended;
    procedure Parse;
    procedure Compile;
    procedure UseStandardFunctions;
    constructor Create;
    destructor Destroy; override;

Events
OnFindVariable: TExprMathOnFindVariable

Properties, Methods and Events description

Formula   Text of the formula.
Result    Result of current evaluation
VarCount   Number of variables
VarByIndex[Idx: Integer] Variable number Idx
VarByName[varName: string] Variable with name = varName

OnFindVariable: Event triggered when an unknown variable is found
GetVarIndex   Returns the index of variable with the name specified
AddFunctionDecl Declares a new external function
ModifyFunctionDecl Redirects a function declaration
ResultNOCompile Result of current evaluation without compiling code.
Parse    Invokes explicit formula parse.
    Should be called only once after setting formula.
Compile   Invokes explicit formula compilation.It is called      automatically the first time a result is requested.
UseStandardFunctions Activates standard functions.
Create    Constructor.
Destroy   Destructor.

Demo version limitations

RyFormulaEval demo version will NOT:
Handle more than 8 distinct variables
Support division or power operations
Allow user to declare external functions with more than one parameter.

Code sample

This a sample that demonstrates the use of independent computation threads,

UnitThreads.pas
***********************************************************************
unit UnitThreads;
interface
uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs, RYFormulaEvaluator, StdCtrls, ExtCtrls;

type
TComputationThread = class(TThread)
private
    aExpr: TRyFormulaEval;
    procedure FindVar(VariableName: string; var Value: Extended);
public
    LastResult: Extended;
    procedure Execute; override;
    constructor Create(Susp: Boolean);
    destructor Destroy; override;
end;
TForm2 = class(TForm)
    Button1: TButton;
    Label1: TLabel;
    Lblnum: TLabel;
    Memo1: TMemo;
    Timer1: TTimer;
    procedure Button1Click(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
    procedure Timer1Timer(Sender: TObject);
private
    { Private declarations }
    l: TList;
    Num: Integer;
public
    { Public declarations }
end;
var
Form2: TForm2;

implementation
{$R *.DFM}
{ TComputationThread }

constructor TComputationThread.Create(Susp: Boolean);
begin
inherited Create(True);
aExpr := TRyFormulaEval.Create;
aExpr.UseStandardFunctions;
aExpr.OnFindVariable := FindVar;
aExpr.Formula := 'PERCENT(x, MAX(x, y) * MIN(((k))*l+o, u))';
aExpr.Parse;
Priority := tpNormal;
end;

destructor TComputationThread.Destroy;
begin
aExpr.Free;
inherited;
end;

procedure TComputationThread.Execute;
begin
while not Terminated do
begin
LastResult := aExpr.Result;
sleep(20);
end;
end;

procedure TComputationThread.FindVar(VariableName: string;
var Value: Extended);
begin
if VariableName = 'x' then
    Value := 10
else   if VariableName = 'y' then
    Value := Random(2000)
else   if VariableName = 'k' then
    Value := 30.67
else   if VariableName = 'l' then
    Value := 234
else   if VariableName = 'o' then
    Value := 567
else   if VariableName = 'u' then
    Value := 2.245;
end;

procedure TForm2.Button1Click(Sender: TObject);
var
ct: TComputationThread;
begin
ct := TComputationThread.Create(True);
ct.Resume;
l.Add(ct);
Inc(Num);
LblNum.Caption := IntToStr(Num);
end;

procedure TForm2.FormCreate(Sender: TObject);
begin
l := TList.Create;
Num := 0;
end;

procedure TForm2.FormDestroy(Sender: TObject);
var
t: TThread;
begin
while l.Count > 0 do
begin
   t := l.Items[0];
   t.Terminate;
   t.WaitFor;
   t.Free;
   l.Delete(0);
end;
l.Free;
end;

procedure TForm2.Timer1Timer(Sender: TObject);
var
k: Integer;
t: TComputationThread;
begin
if Assigned(l) and (l.Count > 0) then
begin
    if Memo1.Lines.Count > 200 then
      Memo1.Lines.Clear;
    Memo1.Lines.Add('-----------------------------------------');
    for k := 0 to l.Count-1 do
    begin
      t := l.Items[k];
      Memo1.Lines.Add('THR'+ Format('%4.4d=%f', [k, t.LastResult]));
    end;
    Memo1.Lines.Add('-----------------------------------------');
end;
end;
end.

UnitThreads.dfm
***********************************************************************
object Form2: TForm2
Left = 157
Top = 295
Width = 396
Height = 251
Caption = 'RYFormula Evaluator thread test'
Color = clBtnFace
Font.Charset = DEFAULT_CHARSET
Font.Color = clWindowText
Font.Height = -11
Font.Name = 'MS Sans Serif'
Font.Style = []
OldCreateOrder = False
OnCreate = FormCreate
OnDestroy = FormDestroy
PixelsPerInch = 96
TextHeight = 13
object Label1: TLabel
    Left = 192
    Top = 8
    Width = 64
    Height = 13
    Caption = 'NumThreads:'
end
object Lblnum: TLabel
    Left = 264
    Top = 8
    Width = 32
    Height = 13
    Caption = 'lblNum'
end
object Button1: TButton
    Left = 16
    Top = 8
    Width = 153
    Height = 25
    Caption = 'Add computation thread !'
    TabOrder = 0
    OnClick = Button1Click
end
object Memo1: TMemo
    Left = 16
    Top = 48
    Width = 353
    Height = 169
    Lines.Strings = (
      '')
    TabOrder = 1
end
object Timer1: TTimer
    Interval = 200
    OnTimer = Timer1Timer
    Left = 336
    Top = 8
end
end

License Agreement
This code is shareware. No warranties, express or implied, are provided. The author is not responsible for any problems caused by this component. Use it at your own risk. The author provides no support whatsoever, and is not obligated to any person or corporation for anything related to this software. The author reserves all rights concerning this code. You are free to evaluate it and distribute it for evaluation purposes, if you do not modify any part of it and you distribute all the files as a whole. This code cannot be sold for any purposes, or included in a commercial collection, without the express written consent of the author.
This License Agreement applies to demo version only, please read the the registration section for more information. By installing these files on your computer, you agree to all above conditions.

(C)opyright 2000, Reinaldo Yañez Arrey.
Buenos Aires, Argentina.
rya@labs.df.uba.ar
ryaayr@yahoo.com