fix(basehist): normalize negative integer indices#699
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Thread the per-axis id into _loc_shortcut so plain negative ints in slice bounds and direct access (h[-2], h[1:-2]) are normalized against the axis length, matching NumPy semantics. Complex/loc/rebin indices are untouched. Closes #559. Assisted-by: ClaudeCode:claude-opus-4.8
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* fix: normalize negative integer slice bounds in indexing Negative slice bounds raised `ValueError: begin < end required` (e.g. `h[1:-2]`) because plain negative ints were passed straight to Boost.Histogram, which does not apply NumPy-style negative indexing. `Axis._process_callable` now normalizes plain negative ints relative to the axis length, like Python/NumPy. Locators (`bh.loc`, `bh.tag.at`, rebin/sum steps) are callables handled earlier and stay untouched. The fix flows through `_process_loc`, so it applies to both `__getitem__` and `__setitem__`. Scalar negative indexing already worked via `_compute_uhi_index`. Mirrors scikit-hep/hist#699, fixing the bug at the underlying layer. Assisted-by: ClaudeCode:claude-opus-4.8 * feat: clamp out-of-range slice bounds to match NumPy Out-of-range slice bounds now clamp to [0, len] like NumPy slicing (e.g. h[5:100] -> h[5:], h[-15:5] -> h[:5]), instead of relying on Boost's internal behavior or raising low-level errors. NumPy returns an empty array for slices like h[1:-15] or h[5:2], but a Boost.Histogram axis cannot have zero bins. These now raise a clear IndexError explaining the limitation instead of the cryptic "begin < end required" / "bins > 0 required". The check lives in _handle_slice so that intentional flow access via integration (e.g. h[3::sum] summing the overflow) is preserved. Assisted-by: ClaudeCode:claude-opus-4.8 * ci: pin numpy<2.5 in hist nox session numpy 2.5's stubs use a `type X = ...` statement that mypy rejects under the downstream hist session ("Type statement is only supported in Python 3.12 and greater"), failing the Hist 3.14 job. Pin numpy below 2.5 until the toolchain catches up. Assisted-by: ClaudeCode:claude-opus-4.8 * style: pre-commit fixes --------- Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
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Closes #559.
Negative slice bounds raised
ValueError: begin < end required(e.g.h[1:-2]) because plain negative ints were passed straight to boost-histogram, which does not apply NumPy-style negative indexing._loc_shortcutnow threads the per-axis id through to slice bounds and normalizes plain negativeint/np.integeragainst the axis length.bool,complex(by-value /loc),None, rebinstep, etc. are untouched.Test:
tests/test_general.py::test_negative_index_access—h[-1]==h[9],h[1:-2]==h[1:8],h[-3:-1]==h[7:9], dict-form equivalents, and a two-axis per-axis-length case. Confirmed failing before, passing after.