functions?

[Neutronium]

Hello, I'm currently making a basic Spelunky mod and learning Gamemaker syntax and built-in variables and functions at the same time.  A few questions:

I noticed that while using the instance_crate function, the object location variables obj.x and obj.y are called directly without 'get' functions?
Do I use instance_exists or object_exists in order to determine if there's a brick, block, tree etc. at that specific square?
Is there a simple argument that I can add to exists that determines if there's an obstacle (which can be in a whole range of objects from blocks to trees)?

Thank you!

[marsgreekgod]

I might be wrong but
instance_exists= means one object (one bullet, not all bullets)
object_exists = one type of object (bullets, not trees)

And there is a drag and drop for "If object is at X Y," but I don't know the code off hand.

[MagiMaster]

You should read the GM8 help first. Go to the index and type in instance_exists and object_exists and you will see that that's all they tell you: whether or not that one thing exists somewhere.

Second, you should look through the existing code. There are a number of functions used for checking whether something is somewhere, depending on the situation. collision_rectangle and instance_position are the two most common (IIRC).