Crafting Interpreters

Created: 2020-08-27T02:40:52.243421

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• Lexical analysis: turning a stream of symbols in to meaningful chunks such as strings, numbers, punctuation pieces.
• Parsing: turning a stream of lexically analyzed chunks in to a meaningful and categorized tree.
• Parsing creates an "abstract syntax tree."
• Static analysis: learns things about a program based on what you can tell without having to run it. For example if a variable appears to ever be used or written to.
• Intermediate representation: a format you convert code in to before turning it in to what it's supposed to be.
• Optimization: walking over code and replacing it with equivalent but better peforming code.
• p-code: "portable" or "bytecode" which can be adapted to run on different CPUs through a "virtual machine."
• Transpiler: converts one set of source code to another set of source code. People will bikeshed about the difference between a compiler and a transpiler.
• Dynamically typed: slots can hold any type of object and the type can change.
• Statically typed: slots can only hold specific types of objects which are specified when the code is written.
• Classes: a set of attributes common to all instances of the class.
• Prototypes: objects which may defer data they do not know to another parent object, but each object is truly its own.
• Context free grammars
• Meta programming: using programs to help write programs.
• Visitor pattern
• Pretty printer: walking a syntax tree and producing code from it.
• Recursive descent parsing
• Talks about variable scoping, implementing closures in an interpreter.
• Pratt parsers. Dispatching on punctuation and looking at operator precedence. Doesn't explain what pratt parsers are in much detail though.
• Mark&Sweep collectors: one phase marks all things which can be seen from a root, another phase frees memory pages which are not properly marked.
• Modulos on numbers which are powers of two can be more optimally implemented as bit masks.
• NAN Boxing

Lexing and Parsing

Lexing turns this:

World henlo: 'Hi.'

In to this:

IDENT(World) IDENT(henlo) COLON STRING(Hi.)

While parsing turns this:

IDENT(World) IDENT(henlo) COLON STRING(Hi.)

In to this:

CALL
OBJECT(World)
FUNCTION(henlo)
PARAMETER(Hi.)