unit2.pas

《Delphi常用数值算法集》的配书源码

unit Unit2;

interface
uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls,unit1, Forms, Dialogs;
procedure CHEBFT(A, B:real; var C:array of real; N:integer);
Function CHEBEV(A, B:real; C:array of real; M:integer; X:real):real;
implementation
procedure CHEBFT(A, B:real; var C:array of real; N:integer);
var
    K,J:integer;  SUM,Y,BMA,BPA,FAC:real;
    F:array[0..50] of real;
const
    NMAX = 50;    PI = 3.14159265358979;
begin
    BMA:=0.5 * (B - A);
    BPA:=0.5 * (B + A);
    For K:=1 To N do
    begin
        Y:=Cos(PI * (K - 0.5) / N);
        F[K]:=FUNC(Y * BMA + BPA);
    end;
    FAC:=2/ N;
    For J:=1 To N do
    begin
        Sum:=0 ;
        For K:=1 To N do
        begin
            Sum:=Sum + F[K] * Cos((PI * (J - 1)) * ((K - 0.5) / N));
        end;
        C[J]:=FAC * Sum;
    end;
end;

Function CHEBEV(A, B:real; C:array of real; M:integer; X:real):real;
var
    D,DD,Y,Y2,SV:real;  J:integer;
begin
    If (X - A) * (X - B) > 0 Then ShowMessage('X not in range.');
    D:=0; 
    DD:=0; 
    Y:=(2* X - A - B) / (B - A);
    Y2:=2* Y;
    For J:=M DownTo 2 do
    begin
        SV:=D;
        D:=Y2 * D - DD + C[J];
        DD:=SV;
    end;
    CHEBEV:=Y * D - DD + 0.5 * C[1];
end;
end.