Pascal Code

    function F(X:real):real;
        begin
            F := X*X*X - 3*X + 2;
        end;

    procedure Secant(P0,P1,Delta,Epsilon:real;
                                var P2,Y2,Dp,Ptwo,Pthree:real;
                                var Cond,K:integer);
        const  Small = 1E-20;
        var  Df,Y0,Y1,RelErr:real;
    begin
        K := 0;
        Cond := 0;
        Y0 := F(P0);
        Y1 := F(P1);
        while (K<Max) and (Cond=0) do
            begin
                Df := (Y1 - Y0)/(P1 - P0);
                if Df = 0 then
                    begin
                        Cond := 1;
                        Dp := P1 - P0;
                        P2 := P1;
                    end
                else
                    begin
                        Dp := Y1/Df;
                        P2 := P1 - Dp;
                    end;
                Y2 := F(P2);
                RelErr := ABS(Dp)/(ABS(P2)+Small);
                if (RelErr <= Delta) then  Cond := 2;
                if (ABS(Y2) < Epsilon) then  Cond := 3;
                if (RelErr <= Delta) and (ABS(Y2) < Epsilon) then
                    Cond := 4;
                P0 := P1;
                P1 := P2;
                Y0 := Y1;
                Y1 := Y2;
                K := K+1;
                if K = 1 then  Ptwo := P1;
                if K = 2 then  Pthree := P1;
            end;
        K := K+1;
    end;

(c) John H. Mathews 2004