1 unstable release
0.0.1 | Sep 11, 2019 |
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#62 in #subset
52KB
1.5K
SLoC
An implementation of a tiny Scheme subset
This is an implementation of a (currently miniscule) subset of R7RS-small. See the examples directory and the smoke testsfor to get an idea of what already works.
The architecture is currently a fairly basic interpreter, with syntax
analysis phase up-front, which will transform the raw S-expressions
into an AST, which is then evaluated. This code sprang from code
intended as an example for using the lexpr
crate to implement a
simple S-expression calculator, and got a bit out of hand 😀.
The current architecture is insufficient to support several major language features of Scheme, such as macros or continuations. The plan is to gradually improve the implementation to make such features possible, before investing in additional features based on the current architecture.
The evolution of poco-scheme will probably be largely guided by the chibi-scheme codebase. chibi-scheme is a full implementation of R7RS-small, written in C, employing a bytecode VM, and using syntactic closures as the basic macro mechanism.
Features already present
- Proper tail calls.
- Garbage collection employing the
gc
crate. define
,lambda
,if
.- Fixnums, and some procedures working on numbers.
- A very crude version of
display
andnewline
, both without port arguments.
Next steps
- Basic cons cell support.
- Implement more syntax in
lexpr
:- Quote syntactic shorthand (i.e.
'
).
- Quote syntactic shorthand (i.e.
- Add a transformation of the AST to some kind of bytecode.
Dependencies
~665KB
~13K SLoC