scheme-rs

FFI bindings to a minimal C s-expression parser. No interpreter, no eval, no macros - just lexing and parsing into a tree you can walk. Built for config/DSL use cases (service definitions, port metadata), not for running Scheme.

Usage

usescheme::{parse,parse_all};letsrc=r#"(service (name "nginx") (deps "network") (backoff 1 2 4 8))"#;letexpr=parse(src).unwrap();println!("{:?}",expr);fortop_levelinparse_all(src){foritemintop_level.items(){// walk pairs
}}

Types

pubenum Expr{Sym(String),Str(String),Num(i64),Float(f64),Bool(bool),Pair(Box<Expr>,Box<Expr>),Nil,}

Cons-cell pairs, not vectors - .items() walks a proper list into a Vec<&Expr> for convenience. Improper lists ((a b . c)) will silently drop the tail; don't feed it those.

as_sym, as_str, as_num, as_float, as_bool give you Option<_> accessors instead of matching by hand every time.

Supported syntax

• Symbols: foo, on-failure
• Strings: "daemon off;" (basic escape handling)
• Integers: 1, -4
• Floats: 1.5
• Booleans: #t, #f
• Lists: (a b c), nested freely
• Comments: ; line comment

No quoting, no vectors, no chars, no bignums. If you need more than this, you want a real Scheme implementation, not this.

Build

Vendors and compiles a small C parser (vendor/scheme.c) via cc at build time. No system dependency on a Scheme runtime, no dynamic linking.

License

WTFPL.