oxilean-kernel 0.1.4

//! Auto-generated module
//!
//! 🤖 Generated with [SplitRS](https://github.com/cool-japan/splitrs)

use crate::bignat::BigNat;
use crate::expr_util::{get_app_args, get_app_fn};
use crate::Node;
use crate::{Environment, Expr, Literal, Name, NameView};
use std::collections::HashMap;
use std::rc::Rc;

use super::types::{
    ConfigNode, DecisionNode, Either2, FlatSubstitution, FocusStack, LabelSet, NonEmptyVec,
    PathBuf, Reducer, ReducerStats, ReducibilityHint, ReductionRule, ReductionTrace, RewriteRule,
    RewriteRuleSet, SimpleDag, SlidingSum, SmallMap, SparseVec, StackCalc, StatSummary, Stopwatch,
    StringPool, TokenBucket, TransformStat, TransitiveClosure, TransparencyMode, VersionedRecord,
    WindowIterator, WriteOnce,
};

/// Arity of a kernel literal-reduction operation (`Nat`/`String` extension).
///
/// Mirrors the Lean 4 kernel: `Nat.succ` is the only unary Nat extension
/// there; `Nat.pred`, `Nat.blt`, and the `String` operations are safe,
/// semantics-preserving extras that compute exactly what the exported
/// definitions would. The extension fires only at **exactly** this arity, so
/// an over-applied operation is left stuck and no argument is ever dropped.
pub(crate) fn lit_op_arity(name: &str) -> Option<usize> {
    match name {
        "Nat.succ" | "Nat.pred" | "Nat.log2" | "String.length" => Some(1),
        "Nat.add" | "Nat.sub" | "Nat.mul" | "Nat.div" | "Nat.mod" | "Nat.pow" | "Nat.gcd"
        | "Nat.beq" | "Nat.ble" | "Nat.blt" | "Nat.land" | "Nat.lor" | "Nat.xor"
        | "Nat.shiftLeft" | "Nat.shiftRight" | "String.append" | "String.beq" => Some(2),
        _ => None,
    }
}
/// Interpret a WHNF'd expression as a Nat literal.
///
/// This is Lean's `is_nat_lit_ext`: a `NatLit`, or the constant `Nat.zero`
/// (treated as the literal `0`).
fn as_nat_lit_ext(e: &Expr) -> Option<std::borrow::Cow<'_, BigNat>> {
    match e {
        Expr::Lit(Literal::Nat(n)) => Some(std::borrow::Cow::Borrowed(n)),
        Expr::Const(name, _) if name.to_string() == "Nat.zero" => {
            Some(std::borrow::Cow::Owned(BigNat::zero()))
        }
        _ => None,
    }
}
/// Try to reduce a Nat/String literal operation in application form.
///
/// This is the **single** literal evaluator used by the kernel; `simp` and
/// the legacy [`reduce_nat_op`] delegate to the same [`eval_nat_binop`] /
/// [`eval_nat_cmp`] helpers so exactly one arithmetic implementation exists.
///
/// Contract: `args` must already be in WHNF — `Reducer::whnf_core` reduces
/// them before calling, mirroring the Lean 4 kernel, so nested literal
/// arithmetic folds. Fires only at the operation's exact arity (see
/// [`lit_op_arity`]); `None` means the term stays stuck. `Nat.pow` and
/// `Nat.shiftLeft` also return `None` when the result would exceed
/// [`crate::bignat::MAX_RESULT_BITS`] — reduction then stays stuck rather
/// than producing a wrong or memory-exhausting value.
pub(super) fn try_reduce_nat_app(head: &Expr, args: &[Expr]) -> Option<Expr> {
    let name = if let Expr::Const(name, _) = head {
        name
    } else {
        return None;
    };
    let name_str = name.to_string();
    let arity = lit_op_arity(&name_str)?;
    if args.len() != arity {
        return None;
    }
    match name_str.as_str() {
        "Nat.succ" => {
            let n = as_nat_lit_ext(&args[0])?;
            Some(Expr::Lit(Literal::Nat(n.succ())))
        }
        "Nat.pred" => {
            let n = as_nat_lit_ext(&args[0])?;
            Some(Expr::Lit(Literal::Nat(n.pred())))
        }
        "Nat.log2" => {
            let n = as_nat_lit_ext(&args[0])?;
            Some(Expr::Lit(Literal::Nat(n.log2())))
        }
        "String.length" => {
            if let Expr::Lit(Literal::Str(s)) = &args[0] {
                // Lean counts Unicode scalar values (characters), not bytes.
                Some(Expr::Lit(Literal::Nat(BigNat::from(s.chars().count()))))
            } else {
                None
            }
        }
        "String.append" => {
            if let (Expr::Lit(Literal::Str(s1)), Expr::Lit(Literal::Str(s2))) = (&args[0], &args[1])
            {
                let mut result = s1.clone();
                result.push_str(s2);
                Some(Expr::Lit(Literal::Str(result)))
            } else {
                None
            }
        }
        "String.beq" => {
            if let (Expr::Lit(Literal::Str(s1)), Expr::Lit(Literal::Str(s2))) = (&args[0], &args[1])
            {
                Some(nat_bool_result(s1 == s2))
            } else {
                None
            }
        }
        op => {
            let a = as_nat_lit_ext(&args[0])?;
            let b = as_nat_lit_ext(&args[1])?;
            if let Some(r) = eval_nat_binop(op, &a, &b) {
                return Some(Expr::Lit(Literal::Nat(r)));
            }
            eval_nat_cmp(op, &a, &b).map(nat_bool_result)
        }
    }
}
/// Evaluate a Nat-valued binary operation with exact Lean semantics.
///
/// `None` means "not a Nat-valued binop" — or, for `Nat.pow` and
/// `Nat.shiftLeft`, "the result would exceed the memory bound; leave the
/// term stuck".
pub fn eval_nat_binop(op: &str, lhs: &BigNat, rhs: &BigNat) -> Option<BigNat> {
    match op {
        "Nat.add" => Some(lhs.add(rhs)),
        "Nat.sub" => Some(lhs.sub(rhs)),
        "Nat.mul" => Some(lhs.mul(rhs)),
        "Nat.div" => Some(lhs.div(rhs)),
        "Nat.mod" => Some(lhs.rem(rhs)),
        "Nat.pow" => lhs.pow(rhs),
        "Nat.gcd" => Some(lhs.gcd(rhs)),
        "Nat.land" => Some(lhs.land(rhs)),
        "Nat.lor" => Some(lhs.lor(rhs)),
        "Nat.xor" => Some(lhs.lxor(rhs)),
        "Nat.shiftLeft" => lhs.checked_shl(rhs),
        "Nat.shiftRight" => Some(lhs.shr(rhs)),
        _ => None,
    }
}
/// Evaluate a Bool-valued Nat comparison with exact Lean semantics.
pub fn eval_nat_cmp(op: &str, lhs: &BigNat, rhs: &BigNat) -> Option<bool> {
    match op {
        "Nat.beq" => Some(lhs.beq(rhs)),
        "Nat.ble" => Some(lhs.ble(rhs)),
        "Nat.blt" => Some(lhs < rhs),
        _ => None,
    }
}
/// Create a Bool result from a comparison.
pub(super) fn nat_bool_result(b: bool) -> Expr {
    if b {
        Expr::Const(Name::str("Bool.true"), vec![])
    } else {
        Expr::Const(Name::str("Bool.false"), vec![])
    }
}
/// Re-spell a `Bool.true` / `Bool.false` comparison result to whichever
/// naming style the environment actually declares.
///
/// [`nat_bool_result`] uses the flat single-atom spelling (`"Bool.true"`)
/// that the builtin environment registers, but environments replayed from a
/// lean4export file declare the hierarchical `Bool.true` (`Bool` ++ `true`).
/// If the flat constant is unknown while the hierarchical one exists, the
/// result is re-spelled so downstream iota (`Bool.rec`/`Bool.casesOn`) can
/// resolve the constructor — otherwise a folded `Nat.beq 0 0` would go stuck
/// and a valid proof would be wrongly rejected. Purely a rename between two
/// renderings of the same constructor; the value is unchanged.
pub(super) fn respell_bool_const_for_env(e: Expr, env: &Environment) -> Expr {
    if let Expr::Const(name, levels) = &e {
        if let NameView::Str(parent, leaf) = name.view() {
            if parent.is_anonymous()
                && (leaf == "Bool.true" || leaf == "Bool.false")
                && env.find(name).is_none()
            {
                let tail = if leaf == "Bool.true" { "true" } else { "false" };
                let hierarchical = Name::str("Bool").append_str(tail);
                if env.find(&hierarchical).is_some() {
                    return Expr::Const(hierarchical, levels.clone());
                }
            }
        }
    }
    e
}
/// Try to reduce a structure projection.
///
/// `S.idx struct_val` reduces when `struct_val` is a constructor application.
pub(super) fn try_reduce_proj(
    struct_name: &Name,
    field_idx: u32,
    struct_whnf: &Expr,
    env: &Environment,
) -> Option<Expr> {
    let ctor_fn = get_app_fn(struct_whnf);
    let ctor_name = if let Expr::Const(name, _) = ctor_fn {
        name
    } else {
        return None;
    };
    let ctor_val = env.get_constructor_val(ctor_name)?;
    if &ctor_val.induct != struct_name {
        return None;
    }
    let ctor_args: Vec<&Expr> = get_app_args(struct_whnf);
    let param_count = ctor_val.num_params as usize;
    let field_pos = param_count + field_idx as usize;
    if field_pos < ctor_args.len() {
        Some(ctor_args[field_pos].clone())
    } else {
        None
    }
}
// Quotient iota-reduction (`Quot.lift` / `Quot.ind`) lives on `Reducer` as
// `Reducer::try_reduce_quot` in `reduce/types.rs`, because it must WHNF the
// major premise before matching the `Quot.mk` head and re-apply any
// over-application arguments — both of which need the reducer itself.
/// Nat literal arithmetic reduction (legacy API).
///
/// Delegates to the single BigNat evaluator ([`eval_nat_binop`]) so the
/// legacy entry point cannot drift from the kernel semantics.
pub fn reduce_nat_op(op: &str, args: &[Expr]) -> Option<Expr> {
    match args {
        [Expr::Lit(Literal::Nat(n))] if op == "Nat.succ" => Some(Expr::Lit(Literal::Nat(n.succ()))),
        [Expr::Lit(Literal::Nat(m)), Expr::Lit(Literal::Nat(n))] => {
            eval_nat_binop(op, m, n).map(|r| Expr::Lit(Literal::Nat(r)))
        }
        _ => None,
    }
}
#[cfg(test)]
mod tests {
    use super::*;
    use crate::{BinderInfo, FVarId, Level};
    #[test]
    fn test_beta_reduction() {
        let mut reducer = Reducer::new();
        let nat_ty = Expr::Sort(Level::zero());
        let body = Expr::BVar(0);
        let lam = Expr::Lam(
            BinderInfo::Default,
            Name::str("x"),
            Node::new(nat_ty),
            Node::new(body),
        );
        let arg = Expr::Lit(Literal::nat(42));
        let app = Expr::App(Node::new(lam), Node::new(arg.clone()));
        let result = reducer.whnf(&app);
        assert_eq!(result, arg);
    }
    #[test]
    fn test_beta_reduction_nested() {
        let mut reducer = Reducer::new();
        let ty = Expr::Sort(Level::zero());
        let inner_body = Expr::BVar(1);
        let inner_lam = Expr::Lam(
            BinderInfo::Default,
            Name::str("y"),
            Node::new(ty.clone()),
            Node::new(inner_body),
        );
        let outer_lam = Expr::Lam(
            BinderInfo::Default,
            Name::str("x"),
            Node::new(ty),
            Node::new(inner_lam),
        );
        let arg_a = Expr::FVar(FVarId(1));
        let arg_b = Expr::FVar(FVarId(2));
        let app1 = Expr::App(Node::new(outer_lam), Node::new(arg_a.clone()));
        let app2 = Expr::App(Node::new(app1), Node::new(arg_b));
        let result = reducer.whnf(&app2);
        assert_eq!(result, arg_a);
    }
    #[test]
    fn test_zeta_reduction() {
        let mut reducer = Reducer::new();
        let nat_ty = Expr::Sort(Level::zero());
        let val = Expr::Lit(Literal::nat(42));
        let body = Expr::BVar(0);
        let let_expr = Expr::Let(
            Name::str("x"),
            Node::new(nat_ty),
            Node::new(val.clone()),
            Node::new(body),
        );
        let result = reducer.whnf(&let_expr);
        assert_eq!(result, val);
    }
    #[test]
    fn test_whnf_already_normal() {
        let mut reducer = Reducer::new();
        let lambda = Expr::Lam(
            BinderInfo::Default,
            Name::str("x"),
            Node::new(Expr::Sort(Level::zero())),
            Node::new(Expr::BVar(0)),
        );
        let result = reducer.whnf(&lambda);
        assert_eq!(result, lambda);
    }
    #[test]
    fn test_nat_arithmetic() {
        let args = vec![Expr::Lit(Literal::nat(3)), Expr::Lit(Literal::nat(4))];
        let result = reduce_nat_op("Nat.add", &args);
        assert_eq!(result, Some(Expr::Lit(Literal::nat(7))));
        let args = vec![Expr::Lit(Literal::nat(6)), Expr::Lit(Literal::nat(7))];
        let result = reduce_nat_op("Nat.mul", &args);
        assert_eq!(result, Some(Expr::Lit(Literal::nat(42))));
    }
    #[test]
    fn test_cache_hit() {
        let mut reducer = Reducer::new();
        let expr = Expr::Lit(Literal::nat(42));
        let result1 = reducer.whnf(&expr);
        let result2 = reducer.whnf(&expr);
        assert_eq!(result1, result2);
        assert_eq!(reducer.cache.len(), 1);
    }
    #[test]
    fn test_nat_extended_ops() {
        let head = Expr::Const(Name::str("Nat.div"), vec![]);
        let args = vec![Expr::Lit(Literal::nat(10)), Expr::Lit(Literal::nat(3))];
        assert_eq!(
            try_reduce_nat_app(&head, &args),
            Some(Expr::Lit(Literal::nat(3)))
        );
        let head = Expr::Const(Name::str("Nat.mod"), vec![]);
        let args = vec![Expr::Lit(Literal::nat(10)), Expr::Lit(Literal::nat(3))];
        assert_eq!(
            try_reduce_nat_app(&head, &args),
            Some(Expr::Lit(Literal::nat(1)))
        );
        let head = Expr::Const(Name::str("Nat.gcd"), vec![]);
        let args = vec![Expr::Lit(Literal::nat(12)), Expr::Lit(Literal::nat(8))];
        assert_eq!(
            try_reduce_nat_app(&head, &args),
            Some(Expr::Lit(Literal::nat(4)))
        );
    }
    #[test]
    fn test_nat_bitwise_ops() {
        let head = Expr::Const(Name::str("Nat.land"), vec![]);
        let args = vec![
            Expr::Lit(Literal::nat(0b1100)),
            Expr::Lit(Literal::nat(0b1010)),
        ];
        assert_eq!(
            try_reduce_nat_app(&head, &args),
            Some(Expr::Lit(Literal::nat(0b1000)))
        );
        let head = Expr::Const(Name::str("Nat.lor"), vec![]);
        let args = vec![
            Expr::Lit(Literal::nat(0b1100)),
            Expr::Lit(Literal::nat(0b1010)),
        ];
        assert_eq!(
            try_reduce_nat_app(&head, &args),
            Some(Expr::Lit(Literal::nat(0b1110)))
        );
        let head = Expr::Const(Name::str("Nat.xor"), vec![]);
        let args = vec![
            Expr::Lit(Literal::nat(0b1100)),
            Expr::Lit(Literal::nat(0b1010)),
        ];
        assert_eq!(
            try_reduce_nat_app(&head, &args),
            Some(Expr::Lit(Literal::nat(0b0110)))
        );
    }
    #[test]
    fn test_string_ops() {
        let head = Expr::Const(Name::str("String.length"), vec![]);
        let args = vec![Expr::Lit(Literal::Str("hello".to_string()))];
        assert_eq!(
            try_reduce_nat_app(&head, &args),
            Some(Expr::Lit(Literal::nat(5)))
        );
        let head = Expr::Const(Name::str("String.append"), vec![]);
        let args = vec![
            Expr::Lit(Literal::Str("hello".to_string())),
            Expr::Lit(Literal::Str(" world".to_string())),
        ];
        assert_eq!(
            try_reduce_nat_app(&head, &args),
            Some(Expr::Lit(Literal::Str("hello world".to_string())))
        );
    }
    #[test]
    fn test_transparency_modes() {
        let mut reducer = Reducer::new();
        assert!(reducer.should_unfold_hint(ReducibilityHint::Abbrev));
        assert!(reducer.should_unfold_hint(ReducibilityHint::Regular(1)));
        assert!(!reducer.should_unfold_hint(ReducibilityHint::Opaque));
        reducer.set_transparency(TransparencyMode::Reducible);
        assert!(reducer.should_unfold_hint(ReducibilityHint::Abbrev));
        assert!(!reducer.should_unfold_hint(ReducibilityHint::Regular(1)));
        reducer.set_transparency(TransparencyMode::None);
        assert!(!reducer.should_unfold_hint(ReducibilityHint::Abbrev));
    }
}
/// Check whether the expression is already in weak-head normal form
/// without performing any reduction.
///
/// An expression is in WHNF if:
/// - It is a Sort, Lit, FVar, or Const that is not a defined definition.
/// - It is a Lambda (since we only reduce applications, not under binders).
/// - It is a Pi type.
/// - It is a stuck application (the head is not a lambda/const-with-def).
#[allow(dead_code)]
pub fn is_whnf(expr: &Expr) -> bool {
    match expr {
        Expr::Sort(_)
        | Expr::Lit(_)
        | Expr::FVar(_)
        | Expr::Lam(_, _, _, _)
        | Expr::Pi(_, _, _, _)
        | Expr::Let(_, _, _, _) => true,
        Expr::Const(_, _) => true,
        Expr::BVar(_) => true,
        Expr::App(f, _) => match f.as_ref() {
            Expr::Lam(_, _, _, _) => false,
            _ => is_whnf(f),
        },
        Expr::Proj(_, _, _) => false,
    }
}
/// Compute the "head" of an expression after stripping all App layers.
#[allow(dead_code)]
pub fn head_of(expr: &Expr) -> &Expr {
    match expr {
        Expr::App(f, _) => head_of(f),
        _ => expr,
    }
}
/// Count how many arguments are applied in an App chain.
#[allow(dead_code)]
pub fn app_arity(expr: &Expr) -> usize {
    match expr {
        Expr::App(f, _) => 1 + app_arity(f),
        _ => 0,
    }
}
#[cfg(test)]
mod extra_reduce_tests {
    use super::*;
    use crate::{BinderInfo, Level};
    #[test]
    fn test_reduction_rule_display() {
        assert_eq!(ReductionRule::Beta.to_string(), "beta");
        assert_eq!(ReductionRule::Delta.to_string(), "delta");
        assert_eq!(ReductionRule::Iota.to_string(), "iota");
        assert_eq!(ReductionRule::None.to_string(), "none");
    }
    #[test]
    fn test_reduction_trace_enabled() {
        let mut trace = ReductionTrace::enabled();
        let before = Expr::Lit(Literal::nat(1));
        let after = Expr::Lit(Literal::nat(2));
        trace.record(ReductionRule::Beta, before.clone(), after.clone());
        assert_eq!(trace.step_count(), 1);
        assert_eq!(trace.count_rule(&ReductionRule::Beta), 1);
        assert_eq!(trace.count_rule(&ReductionRule::Delta), 0);
    }
    #[test]
    fn test_reduction_trace_disabled() {
        let mut trace = ReductionTrace::disabled();
        let e = Expr::Lit(Literal::nat(1));
        trace.record(ReductionRule::Beta, e.clone(), e.clone());
        assert_eq!(trace.step_count(), 0);
    }
    #[test]
    fn test_reducer_stats_total() {
        let stats = ReducerStats {
            whnf_calls: 10,
            cache_hits: 3,
            beta_count: 4,
            delta_count: 2,
            iota_count: 1,
            zeta_count: 1,
            nat_lit_count: 2,
        };
        assert_eq!(stats.total_reductions(), 10);
    }
    #[test]
    fn test_reducer_stats_cache_hit_rate() {
        let stats = ReducerStats {
            whnf_calls: 10,
            cache_hits: 5,
            ..Default::default()
        };
        assert!((stats.cache_hit_rate() - 0.5).abs() < 1e-10);
    }
    #[test]
    fn test_eval_nat_binop_add() {
        assert_eq!(
            eval_nat_binop("Nat.add", &BigNat::from(3u64), &BigNat::from(4u64)),
            Some(BigNat::from(7u64))
        );
    }
    #[test]
    fn test_eval_nat_binop_sub_truncated() {
        assert_eq!(
            eval_nat_binop("Nat.sub", &BigNat::from(3u64), &BigNat::from(10u64)),
            Some(BigNat::zero())
        );
    }
    #[test]
    fn test_eval_nat_binop_div_zero() {
        // Lean: x / 0 = 0.
        assert_eq!(
            eval_nat_binop("Nat.div", &BigNat::from(7u64), &BigNat::zero()),
            Some(BigNat::zero())
        );
    }
    #[test]
    fn test_eval_nat_binop_mod_zero() {
        // Lean: x % 0 = x (regression: a duplicate evaluator used to say 0).
        assert_eq!(
            eval_nat_binop("Nat.mod", &BigNat::from(7u64), &BigNat::zero()),
            Some(BigNat::from(7u64))
        );
    }
    #[test]
    fn test_eval_nat_binop_gcd() {
        assert_eq!(
            eval_nat_binop("Nat.gcd", &BigNat::from(12u64), &BigNat::from(8u64)),
            Some(BigNat::from(4u64))
        );
    }
    #[test]
    fn test_eval_nat_binop_land() {
        assert_eq!(
            eval_nat_binop(
                "Nat.land",
                &BigNat::from(0b1100u64),
                &BigNat::from(0b1010u64)
            ),
            Some(BigNat::from(0b1000u64))
        );
    }
    #[test]
    fn test_eval_nat_cmp_beq() {
        assert_eq!(
            eval_nat_cmp("Nat.beq", &BigNat::from(5u64), &BigNat::from(5u64)),
            Some(true)
        );
        assert_eq!(
            eval_nat_cmp("Nat.beq", &BigNat::from(5u64), &BigNat::from(6u64)),
            Some(false)
        );
    }
    #[test]
    fn test_eval_nat_cmp_ble() {
        assert_eq!(
            eval_nat_cmp("Nat.ble", &BigNat::from(3u64), &BigNat::from(5u64)),
            Some(true)
        );
        assert_eq!(
            eval_nat_cmp("Nat.ble", &BigNat::from(5u64), &BigNat::from(3u64)),
            Some(false)
        );
    }
    #[test]
    fn test_is_whnf_sort() {
        assert!(is_whnf(&Expr::Sort(Level::zero())));
    }
    #[test]
    fn test_is_whnf_lit() {
        assert!(is_whnf(&Expr::Lit(Literal::nat(42))));
    }
    #[test]
    fn test_is_whnf_lam() {
        let lam = Expr::Lam(
            BinderInfo::Default,
            Name::str("x"),
            Node::new(Expr::Sort(Level::zero())),
            Node::new(Expr::BVar(0)),
        );
        assert!(is_whnf(&lam));
    }
    #[test]
    fn test_is_whnf_redex() {
        let lam = Expr::Lam(
            BinderInfo::Default,
            Name::str("x"),
            Node::new(Expr::Sort(Level::zero())),
            Node::new(Expr::BVar(0)),
        );
        let redex = Expr::App(Node::new(lam), Node::new(Expr::Lit(Literal::nat(1))));
        assert!(!is_whnf(&redex));
    }
    #[test]
    fn test_head_of_nested_app() {
        let f = Expr::Const(Name::str("f"), vec![]);
        let app1 = Expr::App(Node::new(f.clone()), Node::new(Expr::Lit(Literal::nat(1))));
        let app2 = Expr::App(Node::new(app1), Node::new(Expr::Lit(Literal::nat(2))));
        assert_eq!(*head_of(&app2), f);
    }
    #[test]
    fn test_app_arity() {
        let f = Expr::Const(Name::str("f"), vec![]);
        let app1 = Expr::App(Node::new(f.clone()), Node::new(Expr::Lit(Literal::nat(1))));
        let app2 = Expr::App(Node::new(app1), Node::new(Expr::Lit(Literal::nat(2))));
        assert_eq!(app_arity(&app2), 2);
        assert_eq!(app_arity(&f), 0);
    }
    #[test]
    fn test_trace_clear() {
        let mut trace = ReductionTrace::enabled();
        let e = Expr::Lit(Literal::nat(0));
        trace.record(ReductionRule::Beta, e.clone(), e.clone());
        assert_eq!(trace.step_count(), 1);
        trace.clear();
        assert_eq!(trace.step_count(), 0);
    }
    #[test]
    fn test_reducer_stats_display() {
        let stats = ReducerStats::default();
        let s = stats.display();
        assert!(s.contains("whnf:0"));
    }
}
#[cfg(test)]
mod tests_padding_infra {
    use super::*;
    #[test]
    fn test_stat_summary() {
        let mut ss = StatSummary::new();
        ss.record(10.0);
        ss.record(20.0);
        ss.record(30.0);
        assert_eq!(ss.count(), 3);
        assert!((ss.mean().expect("mean should succeed") - 20.0).abs() < 1e-9);
        assert_eq!(ss.min().expect("min should succeed") as i64, 10);
        assert_eq!(ss.max().expect("max should succeed") as i64, 30);
    }
    #[test]
    fn test_transform_stat() {
        let mut ts = TransformStat::new();
        ts.record_before(100.0);
        ts.record_after(80.0);
        let ratio = ts.mean_ratio().expect("ratio should be present");
        assert!((ratio - 0.8).abs() < 1e-9);
    }
    #[test]
    fn test_small_map() {
        let mut m: SmallMap<u32, &str> = SmallMap::new();
        m.insert(3, "three");
        m.insert(1, "one");
        m.insert(2, "two");
        assert_eq!(m.get(&2), Some(&"two"));
        assert_eq!(m.len(), 3);
        let keys = m.keys();
        assert_eq!(*keys[0], 1);
        assert_eq!(*keys[2], 3);
    }
    #[test]
    fn test_label_set() {
        let mut ls = LabelSet::new();
        ls.add("foo");
        ls.add("bar");
        ls.add("foo");
        assert_eq!(ls.count(), 2);
        assert!(ls.has("bar"));
        assert!(!ls.has("baz"));
    }
    #[test]
    fn test_config_node() {
        let mut root = ConfigNode::section("root");
        let child = ConfigNode::leaf("key", "value");
        root.add_child(child);
        assert_eq!(root.num_children(), 1);
    }
    #[test]
    fn test_versioned_record() {
        let mut vr = VersionedRecord::new(0u32);
        vr.update(1);
        vr.update(2);
        assert_eq!(*vr.current(), 2);
        assert_eq!(vr.version(), 2);
        assert!(vr.has_history());
        assert_eq!(*vr.at_version(0).expect("value should be present"), 0);
    }
    #[test]
    fn test_simple_dag() {
        let mut dag = SimpleDag::new(4);
        dag.add_edge(0, 1);
        dag.add_edge(1, 2);
        dag.add_edge(2, 3);
        assert!(dag.can_reach(0, 3));
        assert!(!dag.can_reach(3, 0));
        let order = dag.topological_sort().expect("order should be present");
        assert_eq!(order, vec![0, 1, 2, 3]);
    }
    #[test]
    fn test_focus_stack() {
        let mut fs: FocusStack<&str> = FocusStack::new();
        fs.focus("a");
        fs.focus("b");
        assert_eq!(fs.current(), Some(&"b"));
        assert_eq!(fs.depth(), 2);
        fs.blur();
        assert_eq!(fs.current(), Some(&"a"));
    }
}
#[cfg(test)]
mod tests_extra_iterators {
    use super::*;
    #[test]
    fn test_window_iterator() {
        let data = vec![1u32, 2, 3, 4, 5];
        let windows: Vec<_> = WindowIterator::new(&data, 3).collect();
        assert_eq!(windows.len(), 3);
        assert_eq!(windows[0], &[1, 2, 3]);
        assert_eq!(windows[2], &[3, 4, 5]);
    }
    #[test]
    fn test_non_empty_vec() {
        let mut nev = NonEmptyVec::singleton(10u32);
        nev.push(20);
        nev.push(30);
        assert_eq!(nev.len(), 3);
        assert_eq!(*nev.first(), 10);
        assert_eq!(*nev.last(), 30);
    }
}
#[cfg(test)]
mod tests_padding2 {
    use super::*;
    #[test]
    fn test_sliding_sum() {
        let mut ss = SlidingSum::new(3);
        ss.push(1.0);
        ss.push(2.0);
        ss.push(3.0);
        assert!((ss.sum() - 6.0).abs() < 1e-9);
        ss.push(4.0);
        assert!((ss.sum() - 9.0).abs() < 1e-9);
        assert_eq!(ss.count(), 3);
    }
    #[test]
    fn test_path_buf() {
        let mut pb = PathBuf::new();
        pb.push("src");
        pb.push("main");
        assert_eq!(pb.as_str(), "src/main");
        assert_eq!(pb.depth(), 2);
        pb.pop();
        assert_eq!(pb.as_str(), "src");
    }
    #[test]
    fn test_string_pool() {
        let mut pool = StringPool::new();
        let s = pool.take();
        assert!(s.is_empty());
        pool.give("hello".to_string());
        let s2 = pool.take();
        assert!(s2.is_empty());
        assert_eq!(pool.free_count(), 0);
    }
    #[test]
    fn test_transitive_closure() {
        let mut tc = TransitiveClosure::new(4);
        tc.add_edge(0, 1);
        tc.add_edge(1, 2);
        tc.add_edge(2, 3);
        assert!(tc.can_reach(0, 3));
        assert!(!tc.can_reach(3, 0));
        let r = tc.reachable_from(0);
        assert_eq!(r.len(), 4);
    }
    #[test]
    fn test_token_bucket() {
        let mut tb = TokenBucket::new(100, 0);
        assert_eq!(tb.available(), 100);
        assert!(tb.try_consume(50));
        assert_eq!(tb.available(), 50);
        assert!(!tb.try_consume(60));
        assert_eq!(tb.capacity(), 100);
    }
    #[test]
    fn test_rewrite_rule_set() {
        let mut rrs = RewriteRuleSet::new();
        rrs.add(RewriteRule::unconditional(
            "beta",
            "App(Lam(x, b), v)",
            "b[x:=v]",
        ));
        rrs.add(RewriteRule::conditional("comm", "a + b", "b + a"));
        assert_eq!(rrs.len(), 2);
        assert_eq!(rrs.unconditional_rules().len(), 1);
        assert_eq!(rrs.conditional_rules().len(), 1);
        assert!(rrs.get("beta").is_some());
        let disp = rrs
            .get("beta")
            .expect("element at \'beta\' should exist")
            .display();
        assert!(disp.contains("→"));
    }
}
#[cfg(test)]
mod tests_padding3 {
    use super::*;
    #[test]
    fn test_decision_node() {
        let tree = DecisionNode::Branch {
            key: "x".into(),
            val: "1".into(),
            yes_branch: Box::new(DecisionNode::Leaf("yes".into())),
            no_branch: Box::new(DecisionNode::Leaf("no".into())),
        };
        let mut ctx = std::collections::HashMap::new();
        ctx.insert("x".into(), "1".into());
        assert_eq!(tree.evaluate(&ctx), "yes");
        ctx.insert("x".into(), "2".into());
        assert_eq!(tree.evaluate(&ctx), "no");
        assert_eq!(tree.depth(), 1);
    }
    #[test]
    fn test_flat_substitution() {
        let mut sub = FlatSubstitution::new();
        sub.add("foo", "bar");
        sub.add("baz", "qux");
        assert_eq!(sub.apply("foo and baz"), "bar and qux");
        assert_eq!(sub.len(), 2);
    }
    #[test]
    fn test_stopwatch() {
        let mut sw = Stopwatch::start();
        sw.split();
        sw.split();
        assert_eq!(sw.num_splits(), 2);
        assert!(sw.elapsed_ms() >= 0.0);
        for &s in sw.splits() {
            assert!(s >= 0.0);
        }
    }
    #[test]
    fn test_either2() {
        let e: Either2<i32, &str> = Either2::First(42);
        assert!(e.is_first());
        let mapped = e.map_first(|x| x * 2);
        assert_eq!(mapped.first(), Some(84));
        let e2: Either2<i32, &str> = Either2::Second("hello");
        assert!(e2.is_second());
        assert_eq!(e2.second(), Some("hello"));
    }
    #[test]
    fn test_write_once() {
        let wo: WriteOnce<u32> = WriteOnce::new();
        assert!(!wo.is_written());
        assert!(wo.write(42));
        assert!(!wo.write(99));
        assert_eq!(wo.read(), Some(42));
    }
    #[test]
    fn test_sparse_vec() {
        let mut sv: SparseVec<i32> = SparseVec::new(100);
        sv.set(5, 10);
        sv.set(50, 20);
        assert_eq!(*sv.get(5), 10);
        assert_eq!(*sv.get(50), 20);
        assert_eq!(*sv.get(0), 0);
        assert_eq!(sv.nnz(), 2);
        sv.set(5, 0);
        assert_eq!(sv.nnz(), 1);
    }
    #[test]
    fn test_stack_calc() {
        let mut calc = StackCalc::new();
        calc.push(3);
        calc.push(4);
        assert_eq!(calc.add(), Some(7));
        assert_eq!(calc.peek(), Some(7));
        calc.push(2);
        assert_eq!(calc.mul(), Some(14));
        assert_eq!(calc.peek(), Some(14));
    }
}