4.1Object

Objects are logical collections of properties. Each property associates a key value with an arbitrary value of any data type.

Property key values can be used to access or assign properties and their associated arbitrary values.

Dynamic property key values are equal to any value referred to by an Identifier, and can be used to access or assign properties and their associated arbitrary values.

Nested properties may be notated in short‐form such that a Full Stop or period may be placed between each property key value.

Objects must be prefixed with the word “Object”.

4.2Symbol

Symbols are uniqueness types, meaning every symbol is immutable and unique. Symbols are used as dynamic property keys for Objects.

Symbols are prefixed by a single “commercial at” characer.

A Symbol that is created by and is a member of TokenLib.symbols is prefixed by two “commercial at” characters.

4.3String

Strings are finite ordered sequences of zero or more 16‐bit unsigned integer values.

Strings must be both prefixed and postfixed by quotation marks.

4.4Boolean

Booleans must be equal to one of two different values: true or false.

4.5Integer

Integers are whole numbers represented by double‐precision 64‐bit binary format IEEE 754‐2008 values.

Integers which are negative must be notated with a minus sign prefix. Integers which both non‐terminating and infinitely large must be notated with Infinity, or -Infinity for negative numbers.

4.6Float

Floats are non‐whole numbers which are represented by double‐precision 64‐bit binary format IEEE 754‐2008 values.

Floats which are negative must be notated with a minus sign prefix.

4.7Null

null is unchangeable and is always equal to null.

4.8Undefined

undefined is unchangeable and is always equal to undefined.

5.1Transformation Functions

5.2Visitor Functions

6.1Error Handling

6.2Execution Cycle

The core execution cycle is called the Fetch‐Coerce‐Execute cycle, or FCE cycle. The FCE cycle’s programming style and construction is that of Aspect‐Oriented Programming. The FCE Functions are cycle, fetchInstruction, coerceInstruction, and executeInstruction; the VirtualMachine constructor submits the three FCE Functions to an AspectWeaver instance. The AspectWeaver instance is given three Pointcuts labaled with the Strings "fetch", "coerce", and "execute". The labeled Pointcuts expose six Joinpoints in total, such that Functions may be added or removed at six logical points in the control flow before or after each of the three FCE Functions.

6.3Preemption

VirtualMachine is able to interrupt a coroutine which has been compiled by the HertzScript Compiler. Preemption may be performed within cycle before each FCE cycle or via adding a Function after the execute Joinpoint or before the cycle Joinpoint.

6.4Constructor

VirtualMachine(uTokenLib = null) :

1. If uTokenLib is strictly equal to null, then
   • Let this.tokenLib be uTokenLib.
2. Else let this.tokenLib be a new instance of class TokenLib;
3. Let this.detourLib be a new instance of class DetourLib with arguments VirtualMachine and this.tokenLib.
4. Let this.userLib be a new instance of class UserLib with arguments this.tokenLib and this.detourLib.
5. Let this.controlBlock be a new instance of class ControlBlock with arguments this.tokenLib.
6. Let this.lastError be this.tokenLib.symbols.nullSym.
7. Let this.lastRemit be this.tokenLib.symbols.nullSym.
8. Let this.lastInstruction be null.
9. Let this.terminated be false.
10. Let instructions be new instance of class Object.
    • Let instructions.enqueue be this._enqueue.
    • Let instructions.import be Array< this._import >.
    • Let instructions.terminate be this._terminate.
    • Let instructions.vmError be this._vmError.
    • Let instructions.programError be this._programError.
    • Let instructions.fetch be this._fetch.
    • Let instructions.coerce be this._coerce.
    • Let instructions.execute be this._execute.
    • Let instructions.cycle be this._cycle.
    • Let instructions.cycleAsync be this._cycleAsync.
11. Let this.weaver be a new instance of class AspectWeaver with arguments this and instructions.

6.5Prototype Members

6.6Prototype Methods

6.7AspectWeaver

The AspectWeaver class is an Aspect‐oriented program control system which is designed to allow the sequential execution, addition, mutation, and removal of Functions during run‐time. Points at which functions may be added or removed are called Joinpoints, whereas the problem domains which Joinpoints implement are called Pointcuts.

6.8DetourLib

The Babel transformation plugin wraps all function declarations and expressions in detouring functions, and the detour library is a collection of function hooks designed to detour specific types of functions.

Detour functions insert a hooking function which replaces the original function with a special invocation adapter. Upon invoking the adapter a new HertzScript virtual machine is started in‐place, and the original function is run from within it. The original function is assigned to a Symbol property named tokenSym. Each hooking function marks the detour function and original function with special marker Symbols which allow the virtual machine to observe information which would originally only be visible at compile‐time.

The below figure illustrates the path of control flow from a caller function to the original function after it has been detoured.

6.9Kernelizer

The Kernelizer class is a very simple object which assigns arbitrary values directly to itself. This class serves as the base class for the InstructionToken class.

Strings given as an argument list to the constructor indicate the labels of arguments given in an Array via the set method, and can be reset with an arbitrary value via the reset method.

6.10InstructionToken

The InstructionToken class extends the Kernelizer class by assigning String type and Symbol kernSym to itself.

6.11TokenLib

TokenLib is a class which creates and contains InstructionToken instances and marker Symbols.

InstructionToken instances are designed to safely encapsulate userspace data such as functions and their input operands, return/yield values, or no data. All InstructionToken instances are marked by having a special symbol assigned to them called kernSym; if VirtualMachine determines that an object has the symbol as a property, then it assumes that the object is an InstructionToken and attempts to process it.

Each InstructionToken is a single‐instance uniqueness type to reduce memory overhead, because all instances are gauranteed to be thread‐safe and free of race conditions. Because the virtual machine executes in a single thread, each unique InstructionToken instance will be used atomically during a single VirtualMachine fetch‐decode‐execute cycle.

6.12UserLib