Linear interpolation at the scalar one-half is the midpoint, on the constructed plane

Identifier: F:cpoint-lerp-half-is-midpoint
Proof route: kernel-lean
External status: proved
Axiom footprint: Empty

Recorded description

For points x0, x1 of the constructed plane, lerp(x0, x1, CPoint.Scalar.inv2) is CPoint.Equiv-equivalent to midpoint(x0, x1).

Formal statement

theorem CPoint.lerp_half_is_midpoint : ((x0 : CPoint) -> ((x1 : CPoint) -> CPoint.Equiv (CPoint.lerp x0 x1 CPoint.Scalar.inv2) (CPoint.midpoint x0 x1)))

Dependencies

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16 direct dependencies 1 direct dependents Graph shows the first 8 on each side.

Evidence

kernel-CPoint.lerp_half_is_midpoint

Kind: kernel-term
Status: checked

Supports: CPoint.lerp_half_is_midpoint 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 -- CPoint.lerp_half_is_midpoint 2>/dev/null | grep -cE '^CPoint\.lerp_half_is_midpoint[[:space:]]'

Evidence notes

`build_cpoint_prelude` admits CPoint.lerp_half_is_midpoint through the trusted `Kernel::add_declaration` gate, which re-checks the proof term against the stated type, so a line in this tool's output for the exact name is a machine-checked proof having been admitted. `theorem_dependency_inventory` builds creal/complex/cpoint in one run; it exits non-zero for a named filter that matches nothing, and `grep -c` (never `-q`) independently asserts the exact tab-anchored line is present. `--release` is MANDATORY: building the constructed carriers recurses deep enough in a debug build to overflow the default thread stack (measured on this tree: release exits 0, debug SIGABRTs at 134).

footprint-CPoint.lerp_half_is_midpoint

Kind: exhaustive-enumeration
Status: checked

Supports: axiom_footprint: [] -- the cpoint prelude's trusted surface is empty, which bounds CPoint.lerp_half_is_midpoint

Checker command

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

Evidence notes

`nat_axiom_inventory --include-constructed --require-axiom-free cpoint` builds the cpoint environment as its own group and reports `cpoint: axiom=0 opaque=0 quotient=0 total_trusted=0` (re-measured on this tree), covering Axiom, Opaque AND Quotient, not just Declaration::Axiom -- this bounds every individual cpoint theorem's footprint by []. `--include-constructed` is REQUIRED: without it the command exits 1 naming `cpoint` as known but not built this run rather than a silent pass, which is the standing trap of an empty/absent result reading as a strong negative when the tool was never pointed at the subject. `nat_axiom_inventory` now covers `cpoint` directly (re-verified on this tree: `--require-axiom-free cpoint` exits 0 with `cpoint: axiom=0 opaque=0 quotient=0 total_trusted=0`), so the footprint_closure_audit fallback some earlier CPoint facts used is not needed here. `--release` is MANDATORY for the same deep-recursion reason as `theorem_dependency_inventory` (measured on this tree: debug SIGABRTs at 134).

Provenance

{
  "date": "2026-08-25",
  "established_by": "axeyum-lean-kernel build_cpoint_prelude",
  "source": "theorem name and dependency edges from theorem_dependency_inventory (builds creal/complex/cpoint); canonical type and top-level binder arity read via a standalone probe binary depending on axeyum-lean-kernel by path, calling only its public Kernel API (environment(), display_name(), render_lean(), axiom_footprint(), expr_node()) -- no in-tree example prints Complex/CPoint theorem types; crates/ source was not touched to produce this batch; the probe was built and run in the session scratchpad and deleted after use."
}