This member function shifts the invoking function from dx to the right if dx > 0 or from -dx to the left if dx < 0. It has no effect if dx = 0. More precisely, if the invoking function is defined on [xMin,xMax) and dx > 0, the new value of the invoking function is:

• dval on the interval [xMin, xMin+dx),
• for all x in [xMin+dx, xMax), the former value at x-dx.

If dx < 0, the new value of the invoking function is:

• for all x in [xMin, xMax+dx), the former value at x-dx,
• dval on the interval [xMax+dx,xMax).

void Shift(
	double dx,
	double dval
)