What does the superscript "$+$" mean? $(2-x_1^2)^{+} = \max(0,(2-x_1^2)^{+})$

Question

While I am doing a dynamic programming exercise, the suggested answer gives me this: $$(2-x_1^2)^{+} = \max(0,(2-x_1^2)^{+})$$

Why they are equal and what does the plus sign mean?

Answer 1

$h^{+}(x)$ is the function where $h^{+}(x) = h(x)$ iff $h(x) \ge 0$, and where $h^{+}(x) = 0$ iff $h(x) \le 0$.