Parsing out

a Good Parser

Parsing Parsers Outline

• Why Parse and What is a Parser

• Ways to Parse and What we will Parse

• Attempt #1 Regroup and Try Again #2

• Try #3 has got to work

• Never Give Up the Ghost #4

• What Works and What to Watch Out for

Why Parse

• people cannot understand binary data
• computers cannot understand people
• a parser translates from 'people' to 'computer'
• people are less than perfect in writing text
• computers require structural perfection

What is a Parser

• program to convert text into binary data
• but not any text, the text has to follow a grammar
• a grammar is a set of rules (we'll code these up soon)
• the binary data is also called an Abstract Syntax Tree  (AST)

Parts of a Parser

• Lexer (optional)

• A parser generator (grammar compiler) OR a runtime library

• Actions: functions that translate to the  Abstract Syntax Tree  (AST) elements of your choice

All the Ways to Parse

• regular expressions (v)
• parser generators using PEG files
• hand coded (recursive decent) parsers
• parser combinators
• others

(techniques)

What to Parse

• identifiers
• strings "in quotes"
• lists (of identifiers, strings and of course nested lists)
• comments

a modest wish list

Test

Driven

Demo

https://github.com/nmorse/set-parsers-to-stun

canopy

parser generator for languages [python java javascript ruby]

a hand coded parser

with the help of xState (a finite state machine lib)

arcsecond

A set of parser "combinators"

(functions that take other functions as arguments and return (yes) new functions)

Compose them (combine them) into a parser

What Works and What to Watch Out for

Thank You

https://github.com/nmorse/set-parsers-to-stun

https://nearley.js.org/

https://xstate.js.org/viz/

https://github.com/francisrstokes/arcsecond