Function for executing mathematical formulas-Reply to "heyongan"

Problem Source: http://www.cnblogs.com/del/archive/2008/08/16/1268786.html#1289015

In this example, both Delphi 2007 and Delphi 2009 are debugged and run:

Code file:

Unit unit1; interfaceuses windows, messages, sysutils, variants, classes, graphics, controls, forms, dialogs, stdctrls; Type tform1 = Class (tform) button1: tbutton; button2: tbutton; button3: tbutton; Procedure button1click (Sender: tobject); Procedure button2click (Sender: tobject); Procedure button3click (Sender: tobject); end; var form1: tform1; implementation {$ R *. DFM} uses comobj; // The runform function that executes mathematical formulas: // The principle is to use the javascrip script. The code references the format function of Delphi. // The first parameter is the formula, constants in the formula must be identified by ten uppercase letters a B c d e f g h I j. // The second parameter is a parameter array, returns the constant value in order (using a string); // currently, supported functions are listed below. However, in order to distinguish them from the following parameters, they can only be lowercase. function runform (formula: string; const ARGs: array of const): string; const F = 'acos = math. ACOs; '+' Asin = math. asin; '+' atan = math. atan; '+' atan2 = math. atan2; '+ 'ceil = math. ceil; '+' Cos = math. cos; '+' E = math. e; '+' exp = math. exp; '+' floor = math. floor; '+' ln10 = math. ln10; '+ 'ln2 = math. ln2; '+' log = math. log; '+ 'log10e = math. log10e; '+ 'log2e = math. log2e; '+' max = math. max; '+' min = math. min; '+' Pi = math. pi; '+' POW = math. pow; '+' random = math. random; '+' Round = math. round; '+' sin = math. sin; '+' SQRT = math. SQRT; '+' sqrt2 = math. sqrt2; '+' tan = math. tan; '; var Len, buflen: integer; Buffer: array [0 .. 4095] of char; Script: olevariant; I: integer; begin for I: = 0 to 9 do formula: = stringreplace (formula, char (I + 65 ), '%' + inttostr (I) + ': s', [rfreplaceall]); buflen: = length (buffer); If length (formula) = buflen-1 then begin while Len> = buflen-1 do begin Inc (buflen, buflen); Result: = ''; setlength (result, buflen ); {$ ifdef Unicode} Len: = formatbuf (pchar (result), buflen-1, pointer (formula) ^, length (formula), argS); {$ else} Len: = formatbuf (pointer (result) ^, buflen-1, pointer (formula) ^, length (formula), argS); {$ endif} end; setlength (result, Len ); end else setstring (result, buffer, Len); try Script: = createoleobject ('scriptcontrol'); script. language: = 'javascript '; script. executestatement (F + 'str = '+ result); Result: = script. eval ('str'); failed t result: = 'err'; end; {runform function end} // Test 1: note that the second parameter must be procedure tform1.button1click (Sender: tobject); var S: string; begin S: = runform ('(A + B) /(a-B) ', ['6', '4']); {Here A = 6; B = 4} // S: = runform ('(6 + 4)/(6-4)', []); {This can also be} showmessage (s); {5} end; // Test 2: Use case-sensitive commands procedure tform1.button2click (Sender: tobject); var S: string; begin S: = runform ('sin () + cos (B) + Tan (a) ', ['0. 8', '0. 9 ']); showmessage (s); {2.36860461622055} end; // Test 3. Javascript constants can be used, but procedure tform1.button3click (Sender: tobject) must be lowercase letters ); vaR S: string; begin S: = runform ('sqrt (POW (A, 2) ', ['Pi']); showmessage (s); {3.14159265358979} end; end.
 

Form file:

object Form1: TForm1  Left = 0  Top = 0  Caption = 'Form1'  ClientHeight = 130  ClientWidth = 206  Color = clBtnFace  Font.Charset = DEFAULT_CHARSET  Font.Color = clWindowText  Font.Height = -11  Font.Name = 'Tahoma'  Font.Style = []  OldCreateOrder = False  Position = poDesktopCenter  PixelsPerInch = 96  TextHeight = 13  object Button1: TButton    Left = 64    Top = 24    Width = 75    Height = 25    Caption = 'Button1'    TabOrder = 0    OnClick = Button1Click  end  object Button2: TButton    Left = 64    Top = 55    Width = 75    Height = 25    Caption = 'Button2'    TabOrder = 1    OnClick = Button2Click  end  object Button3: TButton    Left = 64    Top = 86    Width = 75    Height = 25    Caption = 'Button3'    TabOrder = 2    OnClick = Button3Click  endend