midpnt.txt

用VB实现数值积分的算法集。包括梯形求积法

Sub MIDPNT(A, B, S, N)
    If N = 1 Then
        S = (B - A) * FUNC(0.5 * (A + B))
        IT = 1
    Else
        IT = 3 ^ (N - 2)
        TNM = IT
        DEL = (B - A) / (3# * TNM)
        DDEL = DEL + DEL
        X = A + 0.5 * DEL
        Sum = 0#
        For J = 1 To IT
            Sum = Sum + FUNC(X)
            X = X + DDEL
            Sum = Sum + FUNC(X)
            X = X + DEL
        Next J
        S = (S + (B - A) * Sum / TNM) / 3#
    End If
End Sub