Let's start with generating flatlands. We'll use the Float3 worldPos() function that returns the position of the block we're currently generating and the Float z(Float3 vec) that returns the z component of a vector.
export Block resultBlock = worldPos()::z() < 20 ? block.core.dirt : block.air;
We define an export variable resultBlock (that we'll be querying from the client application - see Application interface) and set it to block.core.dirt for blocks that are below z 20 or to air for the blocks above. Simple.
The only weird thing is the worldPos()::z() syntax. In WOGLAC, a::func(b, c) is equivalent to func(a, b, c), so we might as well have written z(worldPos()), but in this case, using the :: makes the code more readable. This is similar to the Uniform function call syntax.
What if we want to have multiple layers? Simply use a ternary operator!
Float z = worldPos()::z();
export Block resultBlock =
worldPos()::x() < 0 ? block.air :
z < 10 ? block.core.stone :
z < 19 ? block.core.dirt :
z < 20 ? block.core.grass :
block.air
;
