"CODE" 34150;
"BOOLEAN" "PROCEDURE" ZEROIN(X, Y, FX, TOLX);
"REAL" X, Y, FX, TOLX;
"BEGIN" "INTEGER" EXT;
        "REAL" C, FC, B, FB, A, FA, D, FD, FDB, FDA, W, MB,
        TOL, M, P, Q, DW;
        DW:= DWARF; B:= X; FB:= FX; A:= X:= Y; FA:= FX;
    INTERPOLATE: C:= A; FC:= FA; EXT:= 0;
    EXTRAPOLATE: "IF" ABS(FC) < ABS(FB) "THEN"
        "BEGIN" "IF" C ^= A "THEN" "BEGIN" D:= A; FD:= FA "END";
            A:= B; FA:= FB; B:= X:= C; FB:= FC; C:= A; FC:= FA
        "END" INTERCHANGE;
        TOL:= TOLX; M:= (C + B) * 0.5; MB:= M - B;
        "IF" ABS(MB) > TOL "THEN"
        "BEGIN" "IF" EXT > 2 "THEN" W:= MB "ELSE"
            "BEGIN" TOL:= TOL * SIGN(MB);
                P:= (B - A) * FB; "IF" EXT <= 1 "THEN"
                Q:= FA - FB "ELSE"
                "BEGIN" FDB:= (FD - FB) / (D - B);
                    FDA:= (FD - FA) / (D - A);
                    P:= FDA * P; Q:= FDB * FA - FDA * FB
                "END"; "IF" P < 0 "THEN"
                "BEGIN" P:= -P; Q:= -Q "END";
                W:= "IF" P < DW "OR" P <= Q * TOL "THEN" TOL "ELSE"
                "IF" P < MB * Q "THEN" P / Q "ELSE" MB
            "END"; D:= A; FD:= FA; A:= B; FA:= FB;
            X:= B:= B + W; FB:= FX;
            "IF" ("IF" FC >= 0 "THEN" FB >= 0 "ELSE" FB <= 0) "THEN"
            "GOTO" INTERPOLATE "ELSE"
            "BEGIN" EXT:= "IF" W = MB "THEN" 0 "ELSE" EXT + 1;
                "GOTO" EXTRAPOLATE
            "END"
        "END"; Y:= C;
        ZEROIN:= "IF" FC >= 0 "THEN" FB <= 0 "ELSE" FB >= 0
"END" ZEROIN

        "EOP"