The Method Browser

Rules and Actions

Symbol Table

Appendix B summarized the different versions of the stack machine. This appendix contains tables which index the stack machine compilers for the little language developed in chapters six, seven, and eight. The table entries are linked to the examples, to the documentation, and from there to the sources.

These compilers generate code during recognition, i.e., in the action methods. The action classes extend from example 6/10 (Arithmetic10) to example 6/11 (Control11), 7/4 (Functions04), 7/6 (Parameters06), and 7/9 (Blocks09).

To implement nested functions example 7/13 defines the mix-in Nest13 to extend Blocks09 and support function definitions at greater depth — which requires a static link.

To implement global first-order functions example 8/1 defines the mix-in Global01 to extend Blocks09 and primarily support type checking with function types for variables, functions, parameters, and argument values.

To implement nested functions as argument values example 8/8 defines the mix-in Pass08 to extend Blocks09 and Nest13; the language forbids using functions and results or variables with function values.

Finally, to implement nested first-order functions, example 8/14 defines the mix-in First14 to extend the implementation in example 8/1 and support dynamic memory management for frames.

The Method Browser

The method browser can be used to study the evolution of the action classes and methods and, in particular, to see where a method is first defined.

By default it will load the sources of the implementation of the little language in chapters six through eight, but file parameters can be used in a search string to load JavaScript files from the modules directory.

Patterns are used to extract module, class or mix-in, and method names, and the source text of the methods. The patterns assume a particular coding style, mostly based on white space and nesting.

The names are displayed in a table with columns for modules, classes or mix-ins, methods, and nested methods. Names can be selected by clicking in each column. Multiple selections within a column are considered alternatives, selections across columns must all be satisfied. A column without selections is a wildcard.

Selected names have a darker blue background, names that could be added to a selection have a lighter blue background.

Each column can be scrolled vertically. If the mouse hovers over a column (indicated by a focus border) a keypress will scroll to names with the corresponding initial and the delete key will clear all selections in the column.

A combination of names selects methods which can be displayed, sorted alphabetically by method name, or by class or mix-in. A single method is displayed as soon as it is selected.

An initial selection can be defined by specifying one or more module, item, method, and op parameters in a search string for the page. A show parameter requests immediate display of the selection.

op refers to nested methods, i.e., methods within classes which are nested into top-level classes, e.g., the classes which are used to represent types, variables, and functions in the implementation of the little language. The nested methods are also located by patterns based on coding style.

Grammar Rules and Actions

This table shows how the grammar rules and actions are defined or overridden. Numbers reference the example where a rule was used and ⊕ references action method definitions or overrides.

Symbol Table Entries

Symbol table entries have a common base class Symbol which ensures that every symbol has a name and can reference the owner, i.e., the action class which defines the symbol's class; therefore, the symbol classes are inner classes of an action class as the owner.

Getters in the action classes are used to access the symbol classes because getters can be overwritten in subclasses to silently return extended symbol classes. It should be noted, however, that a reference to a getter can be confused with a reference to a method with the same name, i.e., given the class definition

class X {
  get x () { /* ... */ }
  x () { /* ... */ }
}

the reference (new X()).x is ambiguous; e.g., the Node.js JavaScript compiler will return the method function and not note an error.

Variables

Variable descriptions have a common base class Var which is extended by the various action classes. The table links the properties of the descriptions to the classes and examples where they are defined or overridden. () indicates a method. + indicates that an override references super.

Functions

Function descriptions have a common base class Fun which is extended by the various action classes. The table links the properties of the descriptions to the classes and examples where they are defined or overridden. [] indicates that a property is a list. () indicates a method. + indicates that an override references super.

Blocks

A Block represents a scope of names to support block structure.

Types

There is just one type description class Type and there is a separate, global symbol table typeSymbols for types to allow matching of functions and types on their names. Two type values have reserved names: number describes number values and, for convenience, main describes a function without arguments which returns a number.