Add lift/unlift functions for seqseq dimension conversion - #2
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Add nsv/ensv.py with lift and unlift functions as defined in the ENSV spec. lift collapses a seqseq into a single row using separator semantics (init ∘ spill[String, ''] ∘ map(map(escape))), and unlift recovers the original structure by unescaping and splitting on empty strings. Includes 31 tests covering escaping, empty rows, ragged data, and bidirectional roundtrip properties. https://claude.ai/code/session_01PuxiBkVsjVDzcSopK3kNRg
Rewrite lift to use separator semantics directly instead of going through spill+init. Remove ValueError for empty input (caller's responsibility). Remove lift/unlift from top-level namespace. Add decomposition equivalence test. https://claude.ai/code/session_01PuxiBkVsjVDzcSopK3kNRg
Use existing SAMPLES_DATA from test_utils for roundtrip and decomposition equivalence tests instead of maintaining a separate set of cases. Trim redundant unit tests that are covered by samples. https://claude.ai/code/session_01PuxiBkVsjVDzcSopK3kNRg
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Summary
This PR adds
liftandunliftfunctions to convert between 2D sequences of strings (seqseq) and 1D sequences, enabling dimension reduction/recovery while preserving structural information through escape sequences and empty string delimiters.Key Changes
New module
nsv/ensv.py: Implementslift()andunlift()functionslift(seqseq): Converts a 2D sequence into a 1D sequence by escaping special characters (backslashes, newlines, empty cells) and using empty strings as row delimitersunlift(seq): Recovers the original 2D structure from a lifted sequence by unescaping and splitting on empty string delimitersReader.unescape()andWriter.escape()utilitiesUpdated
nsv/__init__.py: Exportsliftandunliftfunctions for public API accessComprehensive test suite
tests/test_ensv.py:unlift(lift(x)) == xandlift(unlift(y)) == yImplementation Details
lift()requires non-empty input (raisesValueErrorfor empty seqseq since[]is irrepresentable)\\, newlines →\n, empty cells →\https://claude.ai/code/session_01PuxiBkVsjVDzcSopK3kNRg