/toy-lisp-c

Primary LanguageC

Lisp-like language interpreter

Proof of concept to explore low level handling of interpreter and to revisit my rusty C skills.

  • hacky REPL
  • no external libraries (just libc)
  • single and double quoted string with some basic escape characters
  • fixnum using immediate value in pointer (ssize_t - 2 bits)
  • variety of basic functions inspired by Common Lisp specification
    • +, -, *, /, mod, =
    • not
    • list, length, car, cdr, cons, last
    • defvar, setq, let, boundp
    • lambda
    • defun, function - global scope
    • mapcar, reduce
    • funcall, apply,
    • if, progn
    • puts, print, exit
    • backtrace
    • and maybe more
  • separate function and variable namespace (Lisp-2)

Quirks

  • not a single free since it is not needed for proof of concept (reference counting with garbage collector would be next)
  • had some issues with optimization at first but later it didn't cause issues, actually compiling with -O3 not to make pointer tagging work (functions aligned to at least 4 bytes)
  • no negative numbers, have to use (- number)
  • unrecognized numbers are silently parsed as zero
  • no float
  • lambda only binds argument list variables, does not create closure