Thu Nov 4

First order of business

Let's discuss any of this week's homework you'd like to go over :

• 3_03.scm - local state with password bank accounts
• 3_09.scm - environment of fibonnaci functions
• 3_11.scm - environment of local state functions
• 3_12.scm - practice with set-car! , set-cdr!
• 3_13.scm - a cyclic list
• 3_14.scm - "mystery" function : reverse
• 3_21.scm - printing a queue data structure

Second order of business

New topic : start looking at "grammars" and "BNF notation" : how to define a programming language.

resources :

• Matt Might's compiler course
  • grammars, BNF, EBNF
• wikipedia:
  • context free grammar
  • BNF ... varations "extended", "augmented", ...
• what is BNF?
• the Dragon Book - Compilers: Principles, Techniques, and Tools
  • chapter 1 : general intro
  • chapter 2 : section 2.2 , "syntax definition"

I'll go over some of these ideas in class, working through some of the examples in the materials above.

The next topic is "lexers" : how to turn a text string into `[(token-type, value), (token-type, value), ....] which is the first step in interpreting or compiling a computer program.

Please start reading through these materials. I'll choose some exercises before Monday which will be due next Thursday.

to think about

These are a bit open ended so far ... but some of these may turn into assignments. ;)

• What is the BNF grammar for the lisps described in Mary Rose's "Little Lisp" or the "python practice project?"
• Pick one of the math expression grammars described in the resources above. Write an arithmetic expression with at least a dozen terms. Trace through how the grammar rules could generate that expression.
• Using those same rules, generate the first few levels of the tree of all possible expressions.
• Create your own small, simple, minimal programming language syntax - first with some examples, then with a grammar syntax specification. How small but useable can you make it? The building blocks might be things like :
  • math expressions : addition, multiplication, grouping
  • assignment statements : bindings or "memory storage" ... variables
  • function definitions
  • conditionals ... boolean operations
  • strings and operations on strings
  • data structures (arrays or lists or whatever)
  • looping syntax
  • input & output
  • any other built-in functions ?

related resources - compilers, interpreters, interesting languages

• full python grammar
• BNF rules of lisp | Lisp BNF
• Norvig's (How to Write a (Lisp) Interpreter (in Python))
• Simple, but not so simple - calculator interpreter in Guile
• Mary Rose Cook's Little Lisp Interpreter
• python practice projects - lisp interpreter
• I built a lisp compiler | hackernews discussion
• An incremental approach to compiler construction - (academic paper; scheme to x86 compiler in C)
• Lisp implementations (interpreter & compiler, in C, explained)
• A crash course in compilers - (overview article)
• Build your own programming language (overview article; pep talk)
• an overview of lexing and parsing
• lisp in forth | discussion
• wikipedia: Forth (programming language)
• mathematical illustration - a manual of geometry and PostScript

attachments

		last modified	size
	expression_grammar.txt	Thu Nov 04 2021 05:14 pm	870B