CReal.ivt_exact_root_at: the exact-root theorem generalized to an arbitrary target value

Identifier: F:creal-ivt-exact-root-at
Proof route: kernel-lean
External status: Not recorded
Axiom footprint: Empty

Recorded description

CReal.ivt_exact_root_at generalizes CReal.ivt_exact_root from a root of F (Equiv (F c) zero) to a preimage of an arbitrary target y with F a <= y <= F b: there exists c in [a, b] with Equiv (F c) y. It carries the SAME strong hypothesis as ivt_exact_root -- a uniformly positive derivative on all of [a, b] -- because it is built as a direct wrapper: shift F by the constant y to get G := fun z => add (F z) (neg y), whose root is F's y-preimage, and re-run ivt_exact_root on G. No weaker hypothesis is available here than for the y = 0 case; this fact does not relax ivt_exact_root's boundary, it only removes its restriction to a single fixed target.

Formal statement

theorem CReal.ivt_exact_root_at : ((x0 : ((x0 : CReal) -> CReal)) -> ((x1 : ((x1 : CReal) -> CReal)) -> ((x2 : CReal) -> ((x3 : CReal) -> ((x4 : CReal.HasDerivativeOn x0 x1 x2 x3) -> ((x5 : CReal.UniformlyContinuousOn x0 x2 x3) -> ((x6 : CReal.le x2 x3) -> ((x7 : CReal) -> ((x8 : CReal.le (x0 x2) x7) -> ((x9 : CReal.le x7 (x0 x3)) -> ((x10 : AxNat) -> ((x11 : ((x11 : CReal) -> ((x12 : CReal.le x2 x11) -> ((x13 : CReal.le x11 x3) -> CReal.le (CReal.ofRat (Rat.natDivSucc (AxNat.succ AxNat.zero) x10)) (x1 x11))))) -> Exists.{1} CReal (fun (x12 : CReal) => And (CReal.le x2 x12) (And (CReal.le x12 x3) (CReal.Equiv (x0 x12) x7)))))))))))))))

Dependencies

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16 direct dependencies 0 direct dependents Graph shows the first 8 on each side.

Evidence

kernel-CReal.ivt_exact_root_at

Kind: kernel-term
Status: checked

Supports: CReal.ivt_exact_root_at is admitted by the trusted kernel gate with the type recorded in formal.statement.

Checker command

cargo run -q --release -p axeyum-lean-kernel --example theorem_dependency_inventory -- CReal.ivt_exact_root_at 2>/dev/null | grep -cE '^CReal\.ivt_exact_root_at[[:space:]]'

Evidence notes

Two independent failure modes, so the exit status depends on the finding rather than on the run completing: theorem_dependency_inventory exits non-zero when a NAMED filter matches nothing, and grep -c exits 1 printing 0 when the anchored line is absent. Anchored with [[:space:]], never \t -- in a scripted (GNU) grep \t is a literal t. grep -c rather than grep -q, which would SIGPIPE the producer under pipefail. --release is MANDATORY: this tool builds creal/complex/cpoint, which overflow the default debug thread stack.

footprint-CReal.ivt_exact_root_at

Kind: exhaustive-enumeration
Status: checked

Supports: axiom_footprint: [] -- the creal prelude's trusted surface is empty, which bounds CReal.ivt_exact_root_at.

Checker command

cargo run -q --release -p axeyum-lean-kernel --example nat_axiom_inventory -- --include-constructed --require-axiom-free creal

Evidence notes

--require-axiom-free exits non-zero when the named prelude's trusted surface (Axiom + Opaque + Quotient) is not empty, and errors rather than silently passing for a prelude the run never built. A declaration cannot depend on a trusted declaration the environment does not contain, so an empty creal surface bounds every declaration in it, including CReal.ivt_exact_root_at. This is a whole-prelude bound, not a per-declaration measurement; the per-declaration figure is the footprint column of kernel_declaration_projection, measured 0 for this row.

Provenance

{
  "date": "2026-08-27",
  "curation": "curated",
  "generated_by": "scripts/gen-kernel-facts.py",
  "established_by": "axeyum-lean-kernel build_creal_prelude (crates/axeyum-lean-kernel/src/creal/)",
  "source": "Derived mechanically from the unfiltered emit of `cargo run -q --release -p axeyum-lean-kernel --example kernel_declaration_projection`, which prints one TSV row per declaration whose fields are (prelude, kind, display name, axiom-footprint size, direct type declarations, direct declarations, direct theorems, Kernel::render_lean(declaration.ty())). formal.statement is that last field verbatim; depends_on is the direct-theorem column intersected with this ledger's registered facts; axiom_footprint is the footprint-size column, cross-checked by the whole-prelude nat_axiom_inventory run recorded in the second evidence row. No field was hand-transcribed and no prose was authored."
}