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)
• string representation by rope data structure
• 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)

Libraries

- `(scheme base)`
- `(scheme write)`
- `(scheme cxr)`
- `(scheme file)`
- `(scheme inexact)`
- `(scheme time)`
- `(scheme process-context)`
- `(scheme load)`
- `(scheme lazy)`
- `(picrin macro)`

    - `define-macro`
    - `gensym`
    - `macroexpand`

        Old-fashioned macro.

    - `make-syntactic-closure`
    - `identifier?`
    - `identifier=?`

        Syntactic closures.

    - `er-macro-transformer`
    - `ir-macro-transformer`

        Explicit renaming macro family.

- `(picrin regexp)`

    - `(regexp? obj)`
    - `(regexp ptrn [flags])`

        Compiles pattern string into a regexp object. A string `flags` may contain any of #\g, #\i, #\m.

    - `(regexp-match re input)`

        Returns two values: a list of match strings, and a list of match indeces.

    - `(regexp-replace re input txt)`
    - `(regexp-split re input)`

- `(picrin user)`

	When you start the REPL, you are dropped into here.

- `(srfi 1)`

    List manipulation library.

- `(srfi 95)`

    Sorting and Marging.

The REPL

At the REPL start-up time, some usuful built-in libraries listed below will be automatically imported.

• (scheme base)
• (scheme load)
• (scheme process-context)
• (scheme write)
• (scheme file)
• (scheme inexact)
• (scheme cxr)
• (scheme lazy)
• (scheme time)

Compliance with R7RS

section	status	comments
2.2 Whitespace and comments	yes
2.3 Other notations	incomplete	#e #i #b #o #d #x
2.4 Datum labels	yes
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. TODO: multiple argument for unquote
4.2.9 Case-lambda	N/A
4.3.1 Bindings constructs for syntactic keywords	incomplete	(*1)
4.3.2 Pattern language	yes	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	yes
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	incomplete	only partial support supplied.
6.3 Booleans	yes
6.4 Pairs and lists	yes	list? is safe for using against circular list.
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	raise-continuable is not supported
6.12 Environments and evaluation	N/A
6.13.1 Ports	yes
6.13.2 Input	incomplete	TODO: binary input
6.13.3 Output	yes
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

IRC

There is a chat room on chat.freenode.org, channel #picrin.

How to use it

• make Makefile

  Change directory to build then run cmake to create Makefile. Once Makefile is generated you can run make command to build picrin.

    $ cd build
    $ cmake ..
  

  Of course you don't need to move to build directory before running cmake (in that case $ cmake .), but I strongly recommend to follow above instruction.

• build

  A built executable binary will be under bin/ directory and shared libraries under lib/.

    $ make
  

  If you are building picrin on other systems than x86_64, PIC_NAN_BOXING flag is automatically turned on (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

  If you execute cmake with debug flag -DCMAKE_BUILD_TYPE=Debug, it builds the binary with all debug flags enabled (PIC_GC_STRESS, VM_DEBUG, DEBUG).

    $ cmake -DCMAKE_BUILD_TYPE=Debug ..
  

• install

  As of this writing 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. (TODO)

Requirement

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

• lex (preferably, flex)
• getopt
• readline (optional)
• regex.h of POSIX.1 (optional)

Optional libraries are, if cmake detected them, automatically enabled. The compilation is tested only on Mac OSX and Ubuntu. I think (or hope) it'll be ok to compile and run on other operating systems such as Arch or Windows, but I don't guarantee :(

Authors

See AUTHORS