What the function Calc.Approach(x, y, z) do?

[Perh0nen]

It's been used in many places. Wonder what's the specific meaning it return?

[NoelFB]

It makes X approach Y by a delta of Z, but doesn't overstep it.

float x = 10, y = 23, z = 5;
x = Calc.Approach(x, y, z); // x = 15 now
x = Calc.Approach(x, y, z); // x = 20 now
x = Calc.Approach(x, y, z); // x = 23 now