sim-lib-expr-tree

sim-lib-expr-tree is the loadable runtime library for the SIM expression-tree framework. Loading ExprTreeLib registers the stable expr-tree/* function family, argument and result Shapes, browseable operation Cards, and the reconstructable source and policy classes.

Runtime surface

The library exports:

• lifecycle and namespace operations: open, new-cell, new-dir, mount, unmount, move, rename, and delete;
• source and policy operations: set-expr, set-calc-policy, and set-codec-policy;
• reads and calculation: ref, list, calculate, recalculate, recalculate-recursive, cancel, refresh, status, and explain;
• the bounded standard stream returned by watch.

Each function checks a declared capability before touching a tree: expr-tree.read, expr-tree.write, expr-tree.calculate, or expr-tree.mount. Arity, path, collection, tree-size, and diagnostic bounds keep the public failure surface finite. The Lisp surface preserves the final source argument to new-cell and set-expr as an unevaluated expression, so a source such as (expr-tree/ref "/base") becomes a dependency rather than an eager call.

DurableSourceRecord and DurablePolicyRecord participate in Citizen reconstruction. They contain authored data only. TreeHandle deliberately stays opaque because it carries a live writer scope, backend access, and the session's authority boundary.

Use

use sim_lib_expr_tree::install_expr_tree_lib;

# fn install(cx: &mut sim_kernel::Cx) -> sim_kernel::Result<()> {
install_expr_tree_lib(cx)?;
# Ok(())
# }

The embedding runtime also installs codec/lisp and grants only the capabilities its caller is allowed to exercise. The finite-tree and automatic-and-directed recipes under recipes/ are compiled into the crate and executed verbatim by focused tests.

cargo test -p sim-lib-expr-tree
cargo run -p xtask -- check-recipes