"CODE" 34191;
    "COMMENT" MCA 2421;
    "PROCEDURE" COMVECHES(A, N, LAMBDA, MU, EM, U, V);
    "VALUE" N, LAMBDA, MU;
    "INTEGER" N; "REAL" LAMBDA, MU; "ARRAY" A, EM, U, V;
    "BEGIN" "INTEGER" I, I1, J, COUNT, MAX;
        "REAL" AA, BB, D, M, R, S, W, X, Y, NORM, MACHTOL, TOL;
        "ARRAY" G, F[1:N];
        "BOOLEAN" "ARRAY" P[1:N];

        NORM:= EM[1]; MACHTOL:= EM[0] * NORM; TOL:= EM[6] * NORM;
        MAX:= EM[8];
        "FOR" I:= 2 "STEP" 1 "UNTIL" N "DO"
        "BEGIN" F[I - 1]:= A[I,I - 1]; A[I,1]:= 0 "END";
        AA:= A[1,1] - LAMBDA; BB:= -MU;
        "FOR" I:= 1 "STEP" 1 "UNTIL" N - 1 "DO"
        "BEGIN" I1:= I + 1; M:= F[I];
            "IF" ABS(M) < MACHTOL "THEN" M:= MACHTOL;
            A[I,I]:= M; D:= AA ** 2 + BB ** 2; P[I]:= ABS(M) < SQRT(D);
            "IF" P[I] "THEN"
            "BEGIN" "COMMENT" A[I,J] * FACTOR AND A[I1,J] - A[I,J];
                F[I]:= R:= M * AA / D; G[I]:= S:= -M * BB / D;
                W:= A[I1,I]; X:= A[I,I1]; A[I1,I]:= Y:= X * S + W * R;
                A[I,I1]:= X:= X * R - W * S;
                AA:= A[I1,I1] - LAMBDA - X; BB:= -(MU + Y);
                "FOR" J:= I + 2 "STEP" 1 "UNTIL" N "DO"
                "BEGIN" W:= A[J,I]; X:= A[I,J];
                    A[J,I]:= Y:= X * S + W * R;
                    A[I,J]:= X:= X * R - W * S; A[J,I1]:= -Y;
                    A[I1,J]:= A[I1,J] - X
                "END"
            "END"
            "ELSE"
            "BEGIN" "COMMENT" INTERCHANGE A[I1,J] AND
                A[I,J] - A[I1,J] * FACTOR;
                F[I]:= R:= AA / M; G[I]:= S:= BB / M;
                W:= A[I1,I1] - LAMBDA; AA:= A[I,I1] - R * W - S * MU;
                A[I,I1]:= W; BB:= A[I1,I] - S * W + R * MU;
                A[I1,I]:= -MU;
                "FOR" J:= I + 2 "STEP" 1 "UNTIL" N "DO"
                "BEGIN" W:= A[I1,J]; A[I1,J]:= A[I,J] - R * W;
                    A[I,J]:= W;
                    A[J,I1]:= A[J,I] - S * W; A[J,I]:= 0
                "END"
            "END"
        "END"
        P[N]:= "TRUE"; D:= AA ** 2 + BB ** 2; "IF" D < MACHTOL ** 2
        "THEN" "BEGIN" AA:= MACHTOL; BB:= 0; D:= MACHTOL ** 2 "END";
        A[N,N]:= D; F[N]:= AA; G[N]:= -BB;
        "FOR" I:= 1 "STEP" 1 "UNTIL" N "DO"
        "BEGIN" U[I]:= 1; V[I]:= 0 "END";
        COUNT:= 0;
     FORWARD: "IF" COUNT > MAX "THEN" "GOTO" OUTM;
        "FOR" I:= 1 "STEP" 1 "UNTIL" N "DO"
        "BEGIN" "IF" P[I] "THEN"
             "BEGIN" W:= V[I]; V[I]:= G[I] * U[I] + F[I] * W;
                U[I]:= F[I] * U[I] - G[I] * W; "IF" I < N "THEN"
                "BEGIN" V[I + 1]:= V[I + 1] - V[I];
                    U[I + 1]:= U[I + 1] - U[I]
                "END"
            "END"
            "ELSE"
            "BEGIN" AA:= U[I + 1]; BB:= V[I + 1];
                U[I + 1]:= U[I] - (F[I] * AA - G[I] * BB); U[I]:= AA;
                V[I + 1]:= V[I] - (G[I] * AA + F[I] * BB); V[I]:= BB
            "END"
        "END" FORWARD;
     BACKWARD: "FOR" I:= N "STEP" -1 "UNTIL" 1 "DO"
        "BEGIN" I1:= I + 1;
            U[I]:= (U[I] - MATVEC(I1, N, I, A, U) + ("IF" P[I] "THEN"
            TAMVEC(I1, N, I, A, V) "ELSE" A[I1,I] * V[I1])) / A[I,I];
            V[I]:= (V[I] - MATVEC(I1, N, I, A, V) - ("IF" P[I] "THEN"
            TAMVEC(I1, N, I, A, U) "ELSE" A[I1,I] * U[I1])) / A[I,I]
        "END" BACKWARD;
     NORMALISE: W:= 1 / SQRT(VECVEC(1, N, 0, U, U) +
        VECVEC(1, N, 0, V, V));
        "FOR" J:= 1 "STEP" 1 "UNTIL" N "DO"
        "BEGIN" U[J]:= U[J] * W; V[J]:= V[J] * W "END";
        COUNT:= COUNT + 1; "IF" W > TOL "THEN" "GOTO" FORWARD;
     OUTM: EM[7]:= W; EM[9]:= COUNT
    "END" COMVECHES;
        "EOP"