33 lines
804 B
Plaintext
Executable File
33 lines
804 B
Plaintext
Executable File
#! /usr/bin/env -S jq --from-file --sort-keys --compact-output
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#
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# Models a multiset as a JSON object.
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#
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# Takes an operation which contains actions, each in one of two shapes:
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#
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# Add x:
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#
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# { "+": $x }
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#
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# Remove x:
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#
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# { "-": $x }
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#
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# (where `$x` is a string).
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#
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# These actions are reduced to a multiset represented by an
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# object. The key being the item to count (corresponding to `$x` above),
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# and the value being the count itself (corresponding to how many times
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# `$x` was added, minus how many times `$x` was removed).
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#
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# Errors if any unrecognizable action is encountered.
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#
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# For an example, see `rad-cob-multiset.md`.
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reduce
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.op.actions[]
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as {"+": $p, "-": $m} (
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.value;
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.[$p // $m // ("invalid" | halt_error)] |= (
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[. + (if $p then 1 else -1 end), 0] | max
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)
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)
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