A language in 20 minutes
summary
Claim: a working Lisp engine in 20 minutes that implements arithmetic, conditional logic, variables, user‑defined functions, recursion and lexical closures. Implementation uses a PEG pauser generator called canopy, generates a parse tree, evaluates lists by treating first element as procedure or syntax, and demonstrates factorial = 720 and closures returning functions that capture definition scope. Code and slides are online (slides.jc.com, GitHub). It works as shown but omits floats, strings, macros and tail‑call optimization—useful prototype, not production ready.
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chapters (22)
- 0:00Start
- 4:53Operators
- 5:14Expressions
- 6:34Conditional Logic
- 7:17Closures
- 7:57Pausing Expression Grammar
- 9:30How Does the Evaluation Model Work
- 11:03Syntaxes
- 14:01List Module
- 17:20Evaluation Rule
- 17:49Variables
- 19:37Top-Level Scope
- 19:51Built-In Functions
- 21:39Add a Rule for Parsing Lists
- 23:47Defining Variables
- 26:19Functions
- 26:44Lambda
- 27:49Scheme Function Evaluation
- 29:55Conditional Evaluation
- 33:24Syntax Checking
- 34:01Macros
- 37:56What Would Be Your Opinion of a Language That Gives You Lisp like Capabilities in the Sense of Macros
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