Picrin

Picrin is a lightweight scheme implementation intended to comply with full R7RS specification. Its code is written in pure C99 and does not requires any special external libraries installed on the platform.

Features

• R7RS compatibility (but partial support)
• reentrant design (all VM states are stored in single global state object)
• bytecode interpreter (based on Stack VM)
• direct threaded VM
• Internal representation by Nan-Boxing
• conservative call/cc implementation (users can freely interleave native stack with VM stack)
• exact GC (simple mark and sweep, partially reference count is used as well)
• support full set hygienic macro transformers, including implicit renaming macros
• extended library syntax
• advanced REPL support (multi-line input, etc)
• tiny & portable library (all functions will be in libpicrin.so)

Compliance with R7RS

section	status	comments
2.2 Whitespace and comments	incomplete	block comments are not implemented
2.3 Other notations	incomplete	#e #i #b #o #d #x
2.4 Datum labels	no	unsupported
3.1 Variables, syntactic keywords, and regions
3.2 Disjointness of types	yes
3.3 External representations
3.4 Storage model	yes
3.5 Proper tail recursion	yes	As the report specifies, apply, call/cc, and call-with-values perform tail calls
4.1.1 Variable references	yes
4.1.2 Literal expressions	yes
4.1.3 Procedure calls	yes	In picrin () is self-evaluating
4.1.4 Procedures	yes
4.1.5 Conditionals	yes	In picrin (if #f #f) returns #f
4.1.6 Assignments	yes
4.1.7 Inclusion	incomplete	include-ci. TODO: Once read is implemented rewrite include macro with it.
4.2.1 Conditionals	incomplete	TODO: cond-expand
4.2.2 Binding constructs	yes
4.2.3 Sequencing	yes
4.2.4 Iteration	yes
4.2.5 Delayed evaluation	N/A
4.2.6 Dynamic bindings	yes
4.2.7 Exception handling	no	guard syntax.
4.2.8 Quasiquotation	yes	can be safely nested
4.2.9 Case-lambda	N/A
4.3.1 Bindings constructs for syntactic keywords	incomplete	(*1)
4.3.2 Pattern language	no	syntax-rules
4.3.3 Signaling errors in macro transformers	yes
5.1 Programs	yes
5.2 Import declarations	incomplete	only simple import declarations, no support for import with renaming.
5.3.1 Top level definitions	yes
5.3.2 Internal definitions	yes	TODO: interreferential definitions
5.3.3 Multiple-value definitions	yes
5.4 Syntax definitions	yes	TODO: internal macro definition is not supported.
5.5 Recored-type definitions	no
5.6.1 Library Syntax	incomplete	In picrin, libraries can be reopend and can be nested.
5.6.2 Library example	N/A
5.7 The REPL	yes
6.1 Equivalence predicates	yes	TODO: equal? must terminate if circular structure is given
6.2.1 Numerical types	yes	picrin has only two types of internal representation of numbers: fixnum and double float. It still comforms the R7RS spec.
6.2.2 Exactness	yes
6.2.3 Implementation restrictions	yes
6.2.4 Implementation extensions	yes
6.2.5 Syntax of numerical constants	yes
6.2.6 Numerical operations	yes	denominator, numerator, and rationalize are not supported for now. Also, picrin does not provide complex library procedures.
6.2.7 Numerical input and output	no
6.3 Booleans	yes
6.4 Pairs and lists	yes
6.5 Symbols	yes
6.6 Characters	yes
6.7 Strings	yes	substring is not provided
6.8 Vectors	yes
6.9 Bytevectors	yes
6.10 Control features	yes
6.11 Exceptions	yes	TODO: native error handling
6.12 Environments and evaluation	N/A
6.13.1 Ports	yes
6.13.2 Input	incomplete
6.13.3 Output	yes	TODO: write, write-shared and display are unsafe against circular objects
6.14 System interface	yes

1. Picrin provides hygienic macros in addition to so-called legacy macro (define-macro), such as syntactic closure, explicit renaming macro, and implicit renaming macro. As of now let-syntax and letrec-syntax are not provided.

Homepage

Currently picrin is hosted on Github. You can freely send a bug report or pull-request, and fork the repository.

https://github.com/wasabiz/picrin

How to use it

• build

  A built executable binary will be under bin/ directory and a shared library libpicrin.so under lib/.

    $ make
  

  If you want to build picrin on other systems than x86_64, make sure PIC_NAN_BOXING flag is turned off (see include/config.h for detail).

• run

  Simply directly run the binary bin/picrin from terminal, or you can use make to execute it like this.

    $ make run
  

• debug-run

  When make command is called with an argument debug, it builds the binary with all debug flags enabled (PIC_GC_STRESS, VM_DEBUG, DEBUG).

    $ make debug
  

• install

  As of now picrin does not provide a command automatically installs the binary. If you want to place picrin library and binary in a parmanent directory, please do it by hand.

Requirement

picrin scheme depends on some external libraries to build the binary:

• bison
• yacc
• make
• gcc
• readline

The compilation is tested only on Mac OSX. I think (or hope) it'll be ok to compile and run on other operating systems such as Linux or Windows, but there's no guarantee :(

Authors

See AUTHORS