this repo contains all the files I created while following the awesome tutorial of Write Yourself a Scheme in 48 hours although I gotta admit (and you can see in the commit history) it took me far more than 48 hours. It makes me wonder wether it was 48 person hours instead of calendar hours :p. Nevertheless, If you haven't read it, it's an excellent resource to learn about haskell if you already now lisp, or learn about scheme if you already know haskell.

Some of the code is simply taken from the tutorial, although I manually rewrote almost all code, to work myself through the machinery.

The rest of the code are extra things I wanted to implement, things I changed, and a bunch of the exercises interleaved in the tutorial, a non exhaustive list of things I changed:

• Used Megaparsec instead of Parsec
• Implemented proper string literals, with character escaping.
• Support for oct and hex literals
• Added the full Scheme numeric tower, although I missed some of the polymorphism
• Implemented backquote: quasiquote and quote
• added type testing functions e.g. string?, also removed some of the type coercion, although standard schemes lets it
• symbol-handling functions e.g string->symbol
• implemented cond, (previously, there was case too, but it was removed when the Func in LispVal was added, because Eq is undefined for functions)

This is assuming you have ghc installed (I have version 8.0.1 but probably other versions work too).

compiling: ghc -main-is SchemeRepl -o my_scheme SchemeRepl.hs

there are two ways of using it:

• starting a repl: ./my_scheme running the program without arguments. To exit the Repl use ctrl-D or write quit
• batch mode: ./my_scheme file1.scm the first argument is the file name, the rest of the arguments are binded to variable args inside the program

(there is a third way actually, running runhaskell SchemeRepl.hs this has the advantage of not generating the *.hi and *.o files, but it compiles everytime.

note: both the primitives and the standard library should behave just like the scheme standard specifies

• boolean

  • not

• functions

  • id
  • flip
  • curry
  • compose

• number predicates

  • zero?
  • positive?
  • negative?
  • odd?
  • even?

• lists

  • null?
  • list
  • foldr
  • foldl
  • fold
  • reduce
  • unfold
  • sum
  • product
  • and
  • or
  • max
  • min
  • length
  • reverse
  • memq
  • memv
  • member
  • assq
  • asv
  • assoc
  • map
  • filter

• arithmetic
  • +
  • -
  • *
  • /
  • mod
  • quotient
  • remainder
• numeric boolean
  • =
  • <
  • >
  • /=
  • >=
  • <=
• string boolean
  • string=?
  • string<?
  • string>?
  • string<=?
  • string>=?
• boolean
  • &&
  • ||
• lists
  • car
  • cdr
  • cons
• equality
  • eq?
  • eqv?
  • equal?
• type tests
  • boolean?
  • pair?
  • vector?
  • number?
  • string?
  • char?
  • symbol?
• conversions
  • symbol->string
  • string->symbol
• IO Primitives
  • apply
  • open-input-file
  • open-output-file
  • close-input-port
  • close-output-port
  • read
  • write
  • read-contents
  • read-all

• quote
• if
• cond
• set!
• define
• lambda
• load