phy_collision_x/y is marked as real, but is an array

[Glim888]

Description

phy_collision_x/y is marked as real, but is an array

3a03bac0-6116-42d3-bc57-5f4a87cbc4d9

[Appley-Apple]

I don't know how the GML type system works exactly but this appears to be more than just a documentation issue. On the current beta version I am unable to use array functions on phy_collision_x or phy_collision_y, however I can still index them as if they are arrays. Also, typeof(phy_collision_x) returns "number", not "array" (same for phy_collision_y).

[Glim888]

This is how I use it in RT v2023.11.1.160 to avoid crashes.

[Glim888]

I would like to add an additional error about the phy_collision_points.

If you destroy the instance in the same collision step. Then the phy_collision_points became null (silent crash)

collision event:
instance_destroy();
show_debug_message(phy_collision_x[0]);
--> crash

@DiasFranciscoA

[Appley-Apple]

This is how I use it in RT v2023.11.1.160 to avoid crashes.

Is there a way to handle multiple collision points? Sometimes I get 2 collision points and I'd like to know where both of them are, currently phy_collision_x and phy_collision_y are just numbers so they only tell you about a single point.

[Glim888]

Nah it's an array, but you need to check how long the array is.

[YYBartT]

Built-in arrays aren't "true" arrays, a consequence of that is that they cannot be used with the array functions. The syntax meant to be used is the array syntax with the subscript operator:

var _val = builtin_array[index];  // Looks up value at index "index"

The other syntax:

var _val = builtin_array;  // Looks up value at index 0, does not assign a reference to the built-in array to _val

is supported for backward compatibility, as confirmed by @rwkay.
I updated the manual pages to use the first syntax, since that syntax is the one that avoids confusion (other manual pages for built-in array variables, such as instance_id and view_wport also use this syntax). This syntax does return a real in case of the physics collision arrays, since the element at index 0 in any of those arrays is of type real. Another consequence is that, because of how the second syntax works, typeof(builtin_array) returns the type of the first element in the array (which is "number" in the case of phy_collision_x, phy_collision_y, phy_col_normal_x and phy_col_normal_y).

[alicemoretti]

Verified fixed in the current Beta version of the Manual.

Thank you.