C++ reguła falsi algorytm

const Int MAXIT = 30; Set to the maximum allowed number of iterations.
Doub xl, xh, del;
Doub fl = func( x1 );
Doub fh = func( x2 ); Be sure the interval brackets a root.
if( fl * fh > 0.0 ) throw( "Root must be bracketed in rtflsp" );

if( fl < 0.0 ) { Identify the limits so that xl corresponds to the low
    xl = x1; side.
    xh = x2;
} else {
    xl = x2;
    xh = x1;
    SWAP( fl, fh );
}
Doub dx = xh - xl;
for( Int j = 0; j < MAXIT; j++ ) { False - position loop.
    Doub rtf = xl + dx * fl /( fl - fh ); Increment with respect to latest value.
    Doub f = func( rtf );
    if( f < 0.0 ) { Replace appropriate limit.
        del = xl - rtf;
        xl = rtf;
        fl = f;
    } else {
        del = xh - rtf;
        xh = rtf;
        fh = f;
    }
    dx = xh - xl;
    if( abs( del ) < xacc || f == 0.0 ) return rtf; Convergence.
}
throw( "Maximum number of iterations exceeded in rtflsp" )
}