midsqu.txt

来自「《Delphi常用数值算法集》的配书源码」· 文本 代码 · 共 33 行

Function SQU(X, BB:real):real;
begin
    SQU:=2 * X * FUNC(BB - Sqr(X));
end;
procedure MIDSQU(AA, BB:real; var S:real; N:integer);
var
    A,B,TNM,X,DEL,DDEL,SUM:real; IT,J:integer;
begin
    B:=Sqrt(BB - AA);
    A:=0;
    If N = 1 Then
    begin
        S:=(B - A) * SQU(0.5 * (A + B), BB);
        IT:=1;
    end
    Else
    begin
        IT:=Trunc(Exp((N - 2)*Ln(3)));
        TNM:=IT;
        DEL:=(B - A) / (3 * TNM);
        DDEL:=DEL + DEL;
        X:=A + 0.5 * DEL;
        Sum:=0;
        For J:=1 To IT do
        begin
            Sum:=Sum + SQU(X, BB);
            X:=X + DDEL;
            Sum:=Sum + SQU(X, BB);
            X:=X + DEL;
        end;
        S:=(S + (B - A) * Sum / TNM) / 3;
    end;
end;