Devlog2

Link class is for evaluating links. A link is a statement in form of a.b.c, where all expressions after dots (in this case b and c) are either identifiers¹, indexes² or invocations³. Expression before the dot is anything, even the ternary operator. These expressions are link children.

Link evaluation

Links are resolved iteratively, starting from the first expression. Every evaluated expression returns a property (a type or a primitive). But the first child might be a name of an imported file, therefore it is resolved differently from all the next children.

During dynamic creation of a class it is important to know what parts of the link are assigned. For example:

class Start {
    a = mid.end.endProperty // a is not assigned until mid, end and endProperty are
    mid = Middle()
    mid.end.addedEndProperty = "anotherEndValue" /** it is applicable for
        left hand-side of assignment too. mid and end need to be assigned first
        **/
}
class Middle {
    end = End()
}
class End {
    endProperty = "endValue"
}

Adding state, encountering problems

For convenience, I added these properties to the link instance:

• index: index of currently resolved child
• currentVariable: value of currently resolved child
• currentParent: previously resolved child
• table: symbolTable with currentVariable as variableTable
• initialTable: symbolTable before link evaluation, used to resolve function arguments. It is useful in the following code:

class A {
    a = 0
    b = B()
    fun aFunction() {
        b.bFun(a, b) /** here table will change variableTable to B instance, therefore a and b
            properties will not be found for bFun call. That's why invocation arguments are resolved
            using initialTable
            **/
    }
}
class B {
    fun bFun(arg1,arg2) {
        // do something
    }
}

These variables are cleared after the end of the evaluation. However, I didn’t think about recursive functions:

class A {
    a = if(iter < 5) A() else Nothing()
    iter = if(parent == 0) 0 else parent.iter /** parent is a special property.
        It returns an instance from which this instance is created or 0 **/
    fun str() {return "iter, " + a.str()}
}

class Nothing() {
    fun str() { return "end" }
}

In that case, when calling str(), variable values weren’t cleared. I might’ve come up with some hack, but again, I knew that was bad solution. Link represents a token, it is not a place to store evaluation values. So I moved state to function arguments. Link is still a poorly written class that has bugs. I work on fixing them and refactoring Link.

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