Derive named auxiliary legs in project - #231
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The named `project`, `tryproject`, and `unchecked_project` methods now derive a named auxiliary leg for each surplus axis of the input array, matching the bare graded-space form. A surplus trailing axis is an auxiliary leg the backend added to keep the result symmetry-allowed, for example a flux-canceling charge leg for a charge-shifting operator, and it now comes back as a named dimension. Also qualifies `space`, `dim`, `dual`, and `scalar` as `TK.*` in the TensorKit-extension tests, since `ITensorBase` marks `space` public and it otherwise clashes with the `TensorKit` import.
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## main #231 +/- ##
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The backend derives the space of at most one trailing surplus axis (the flux-canceling leg appended as the last domain axis), so the docstring and comment describe one such axis rather than an arbitrary number.
The metaprogrammed methods now only forward each named-index signature to a `<verb>_nameddims` worker, matching the `mul_nameddims` and `matricize_nameddims` pattern already in this file. The workers hold the strip, lower, reattach logic as plain functions that are easy to read on their own, and one body per verb also covers the empty codomain (since `unnamed.(())` and `name.(())` are both `()`), so the separate empty-codomain method collapses. `name_projected` attaches the names and the aux leg the backend may append.
Use `uniquename(eltype(input_names))` rather than a name instance, matching how the other named-tensor helpers in this file mint fresh names from the dim-name type.
Attach a docstring to each of the three named-index methods describing the named-tensor layer: the index-selected backend, the codomain/domain split, and the derived auxiliary leg. Only `project` carried this docstring before, with the other two mentioned only in its text. A shared fragment is interpolated into all three so they stay in sync.
Loop the surplus-axis aux-leg assertions over all three named-index verbs, not just `project`. They share the `name_projected` path and the docstrings assert all three derive the leg, so cover `tryproject` and `unchecked_project` too.
mtfishman
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Builds `project_aux` and `project_pair` through ITensorBase's named `project`/`tryproject`, which now derive and name the flux-canceling auxiliary leg from a trailing surplus axis (ITensor/ITensorBase.jl#231). The `space.(...)` unwrap, the `Index(TensorAlgebra.axes(...))` re-mint, and the `ITensor(...)` wrap all go away: `project_aux`'s aux fallback becomes a single `project` call, and `project_pair` drops from four functions (bare-space core, `_itensor` wrapper, two named dispatch entries) to one that reads the shared aux off the first result with `last(inds(p1))`. Bumps the ITensorBase compat floor to `0.13.7`.
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Summary
The named
project,tryproject, andunchecked_projectmethods (the ones takingNamedUnitRangeindices) now derive a named auxiliary leg for a surplus axis of the input array. When the array carries one more axis than the codomain and domain indices account for, that trailing axis is an auxiliary leg the backend added to keep the result symmetry-allowed, for example a flux-canceling charge leg for a charge-shifting operator likeCdag. It now comes back as a named dimension with a freshly minted name, so a caller can read it off the result.An operator that shifts charge can then be built directly through
projectby reshaping its dense matrix to a trailing length-1 axis:project(reshape(m, (size(m)..., 1)), (prime(i),), (i,))returns the operator with its flux carried on a named aux index. The bare graded-space form already derived this axis, but the named wrappers passed it through unnamed.Also qualifies
space,dim,dual, andscalarasTK.*in the TensorKit-extension tests.ITensorBasemarksspacepublic, so an unqualifiedusing TensorKit: spaceclashes with it when the tests run in a session that already hasITensorBase'sspacein scope.