mrsch / cppscheme

CPPScheme

Scheme implementation in C++ that depends on C++17s new std::variant and std::optional. Heavily inspired by Write Yourself a Scheme in 48 Hours.

Uses Haskell-like Maybe and Either types.

Tested with gcc 7.2.0 on Linux

Setup

Required dependencies

• editline

Get source

git clone --recursive https://github.com/mrsch/CPPScheme.git

Build

1. Run cmake -E chdir build cmake .. to setup the project
2. Compile with cmake --build build
3. Run main: cd bin && ./main
4. Run ( non existanst :-( )tests: cd bin && ./unit_test

Anti Features

• No proper tail recursion
• No tests
• Not all standard procedures implemented
• Only floats as numbers
• No macros
• Not optimized
• Lots of unnessecary copies

Features

• Haskell like error handling with Either type
• Scheme values as Sum type with std::variant
• Should not leak thanks to std::shared_ptr
• Some standard procedures are implemented directly in Scheme (see resources/stdlib.scm)

Types

• Booleans - #t and #f
• Numbers - floats
• Strings
• Vector - #()
• Lambdas
• Characters - #\t
• Atoms

Primitive Expressions

• [X] define
  • [X] shorthand lambda define
• [X] quote
• [X] lambda
• [X] procedure call
• [X] if
• [X] set!

Derived Expressions

• [X] cond
• [X] case
• [X] and
• [X] or
• [X] let
• [X] begin
• [ ] do
• [ ] named let
• [ ] delay + force
• [ ] quasiquote

Standard Procedures

• [X] apply
• [X] eval
• [X] car
• [X] cdr
• [X] cons
• [X] eqv?
• [ ] eq?
• [ ] equal=

Output

• [X] display

Booleans

• [X] not

Math

• [X] +
• [X] -
• [X] *
• [X] /
• [X] modulo
• [ ] remainder
• [ ] max
• [ ] min
• [ ] abs
• [ ] gcd
• [ ] lcm
• [ ] floor
• [ ] ceiling
• [ ] truncate
• [ ] round
• [ ] expt

Numerical

• [X] =
• [X] <
• [X] >
• [X] <=
• [X] >=
• [X] zero?
• [X] positive?
• [X] negative?
• [X] odd?
• [X] even?
• [ ] min
• [ ] max

Lists

• [X] null?
• [X] length
• [X] reverse
• [X] map (only 1 list)

Additional Procedures

• [X] curry
• [X] id
• [X] flip
• [X] compose
• [X] folds (foldl foldr)
• [X] unfold
• [X] sum
• [X] product
• [X] filter