You can get the value of an objects attributes at compile time using the attribute access operator .@.

For example:

Attributes without an argument will have the value true if they are present, and false otherwise.

@public:
foo ::(){
}

bar ::(){
}

printl(foo.@public);
printl(bar.@public);

$ asa attributes.asa
$ ./build/attributes
true
false

Attributes with an argument will return the value they contain if they are present, and false if they are not present.

@deprecated("Some message"):
foo ::(){
}

@customAttr("example"):
bar ::(){
}

printl(foo.@deprecated);
printl(bar.@customAttr);
printl(bar.@deprecated);

$ asa attr_arguments.asa
$ ./build/attr_arguments
Some message
example
false

While it is easy to get the value of an attribute, you can not use the same method to change the value of an attribute.

@customAttr("example"):
bar ::(){
}

bar.@customAttr = "changed";

$ asa attr_set.asa
$ ./build/attr_set
error[E007]:  Cannot modify value of attribute using access operator `.@`. Did you mean to use `#set_attribute()`?

Because attributes are considered immutable, modifying them at compile time is delegated to compiler directives for meta programming. See #set_attribute.