cljrs-interp 0.1.47

Tree-walking interpreter for clojurust (special forms, macros, destructuring)
Documentation

cljrs-interp

Self-contained tree-walking interpreter for Clojure.

Phase: Core interpreter — implemented. no-gc region/static-sink support (Phases 4–5), blacklist integration (Phase 6), and integration tests (Phase 8) of docs/no-gc-plan.md — implemented.

Purpose

Evaluates Clojure Form ASTs produced by cljrs-reader, managing lexical environments, special forms, function application, and the recur trampoline. Under the no-gc Cargo feature, applies the allocation-context stack protocol (scratch regions for function/loop scopes; StaticArena for static-sink expressions).

File layout

src/
  lib.rs         — crate entry point; re-exports Interpreter
  eval.rs        — top-level eval dispatch; symbol/keyword/collection eval
  special.rs     — special form evaluators: def, defn, defmacro, fn*, if, let*,
                   loop*, recur, quote, var, set!, throw, try, do, ns, require,
                   letfn, in-ns, alias, defprotocol, extend-type, extend-protocol,
                   defmulti, defmethod, defrecord, reify, binding, with-out-str
  apply.rs       — eval_call: macro expansion, native-fn dispatch, CljxFn
                   application, recur trampoline; special env-needing handlers
                   (apply, atom, reset!, swap!, volatile!, vreset!, vswap!,
                   agent, send/send-off, with-bindings*, alter-var-root,
                   vary-meta, find-ns, all-ns, create-ns, ns-aliases, remove-ns,
                   alter-meta!, ns-resolve, resolve, intern, bound-fn*)
  arity.rs       — fresh arity ID generator
  destructure.rs — pattern destructuring (vector, map, & rest)
  macros.rs      — macro expansion helpers
  syntax_quote.rs — syntax-quote (backtick) expansion
  virtualize.rs  — let-chain virtualization: assoc/conj chains → transients
tests/
  no_gc_eval.rs  — (no-gc mode) integration tests: arithmetic, def/defn provenance,
                   function-call region stack, loop/recur accumulation,
                   atom/reset!/swap! static-sink correctness

Public API

eval(form, env) -> EvalResult

Evaluate a single Form in env. Entry point for the interpreter.

eval_call(func_form, arg_forms, env) -> EvalResult

Evaluate a function-call form. Handles macros, native-function special cases, and user-defined CljxFn application with the recur trampoline.

eval_body(forms, env) -> EvalResult

Evaluate a sequence of forms, returning the value of the last one.

eval_loop(args, env) -> EvalResult

Evaluate a loop* form. Under no-gc, pushes a ScratchGuard on each iteration and pops it before the tail expression (recur args or return value) so intermediate allocations are freed per iteration.

eval_defn(args, env) -> EvalResult

Evaluate a defn form. Under no-gc, wraps fn creation in StaticCtxGuard so the CljxFn object lands in the StaticArena.

Special handlers in apply.rs

Each handler evaluates its key expressions under the correct allocation context:

Handler Static-sink guard coverage
handle_atom_call initial value
handle_reset_bang new value
handle_swap_call function return value
handle_volatile initial value
handle_vreset new value
handle_vswap function return value
handle_agent_call initial value
handle_alter_var_root function return value
handle_intern value expression (3-arg form)

Value-level special form helpers (IR interpreter API)

The IR interpreter receives already-evaluated Vec<Value> arguments rather than &[Form] AST nodes. These public functions mirror the handle_* form-level handlers but accept pre-evaluated args, allowing the IR interpreter to implement sentinel operations without hitting the stub errors registered in clojure.core:

Function Operation
eval_swap_bang(args, env) swap! — apply f to atom, store result
eval_volatile(args) volatile! — create a new volatile
eval_vreset_bang(args) vreset! — reset volatile value
eval_vswap_bang(args, env) vswap! — apply f to volatile value, store result
make_delay_from_fn(f, globals, ns) make-delay — wrap zero-arg fn in a Delay
eval_alter_var_root(args, env) alter-var-root — apply f to var root, store result
eval_vary_meta(args, env) vary-meta — apply f to obj metadata
eval_with_bindings_star(args, env) with-bindings* — push binding frame, call f
eval_send_to_agent(args, env) send / send-off — dispatch action to agent

make_lazy_seq_from_fn(f, globals, ns) (already public) creates a LazySeq from a zero-arg callable; the above make_delay_from_fn is the analogous helper for Delay.