sergeych
3908b8ee9f
+String now is indexed with Char instances, size supported +Char type and char constants
73 lines
2.2 KiB
Markdown
73 lines
2.2 KiB
Markdown
# OO implementation in Ling
|
|
|
|
Basic principles:
|
|
|
|
- Everything is an instance of some class
|
|
- Every class except Obj has at least one parent
|
|
- Obj has no parents and is the root of the hierarchy
|
|
- instance has member fields and member functions
|
|
- Every class has hclass members and class functions, or companion ones, are these of the base class.
|
|
- every class has _type_ which is an instances of ObjClass
|
|
- ObjClass sole parent is Obj
|
|
- ObjClass contains code for instance methods, class fields, hierarchy information.
|
|
- Class information is also scoped.
|
|
- We acoid imported classes duplication using packages and import caching, so the same imported module is the same object in all its classes.
|
|
|
|
## Instances
|
|
|
|
Result of executing of any expression or statement in the Ling is the object that
|
|
inherits `Obj`, but is not `Obj`. For example it could be Int, void, null, real, string, bool, etc.
|
|
|
|
This means whatever expression returns or the variable holds, is the first-class
|
|
object, no differenes. For example:
|
|
|
|
1.67.roundToInt()
|
|
1>>> 2
|
|
|
|
Here, instance method of the real object, created from literal `1.67` is called.
|
|
|
|
## Instance class
|
|
|
|
Everything can be classified, and classes could be tested for equivalence:
|
|
|
|
3.14::class
|
|
1>>> Real
|
|
|
|
Class is the object, naturally, with class:
|
|
|
|
3.14::class::class
|
|
1>>> Class
|
|
|
|
Classes can be compared:
|
|
|
|
assert(1.21::class == Math.PI::class)
|
|
assert(3.14::class != 1::class)
|
|
assert(π::class == Real)
|
|
π::class
|
|
>>> Real
|
|
|
|
Note `Real` class: it is global variable for Real class; there are such class instances for all built-in types:
|
|
|
|
assert("Hello"::class == String)
|
|
assert(1970::class == Int)
|
|
assert(true::class == Bool)
|
|
assert('$'::class == Char)
|
|
>>> void
|
|
|
|
More complex is singleton classes, because you don't need to compare their class
|
|
instances and generally don't need them at all, these are normally just Obj:
|
|
|
|
null::class
|
|
>>> Obj
|
|
|
|
At this time, `Obj` can't be accessed as a class.
|
|
|
|
|
|
### Methods in-depth
|
|
|
|
Regular methods are called on instances as usual `instance.method()`. The method resolution order is
|
|
|
|
1. this instance methods;
|
|
2. parents method: no guarantee but we enumerate parents in order of appearance;
|
|
3. possible extension methods (scoped)
|