Add support for combination queries on same snapshot point #439
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Allow for return_keys of logical combinations of queries
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| OR : {token, {'UNION', TokenLine}}. | ||
| AND : {token, {'INTERSECT', TokenLine}}. | ||
| NOT : {token, {'SUBTRACT', TokenLine}}. |
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Kind, of, NOT is in fact a unary operation and SUBTRACT a binary.
This might cause future confusion. If you write NOT $d, then you mean to say the universe apart from whatever is in $d. But the universe is not part of your language.
- But more prominently, if I write
$a SUBTRACT NOT $byou fail, whereas in set theory you would take the complenet from B and subtract that from A.
It will be hard to implement complement. So not sure you want to add NOT. Also because NOT is very hard to do in regular expressions.
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In many applications this parser would have a "normalize" function that applies "De Morgan" laws to normalize the SET. This may simplify the final regular expression building, but may be considered out of scope here.
| INTERSECT : {token, {'INTERSECT', TokenLine}}. | ||
| SUBTRACT : {token, {'SUBTRACT', TokenLine}}. | ||
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| \$[1-8]+ : {token, {set_id, TokenLine, strip_identifier(TokenChars)}}. |
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This feels limiting... zero and nine cannot be in the set_id? Do you actually mean a number not starting with zero?
\$[1-9][0-9]*
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In particular since you take the "nth" set_id from a list, missing the "9" is confusing if you allow "11".
I like the map you use in filters better, then it does not really matter what representation you use. Is that possible here as well, to provide apply_setop with a map of set_id to the actual set?
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| apply_setop({setop, SetOp}, SetList) -> | ||
| apply_setop(SetOp, SetList); | ||
| apply_setop( |
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base case missing:
apply_setop({set_id, _, SetID}, SetList) ->
lists:nth(SetID, SetList)
This follows from
9> F = leveled_setop:generate_setop_function("$1").
#Fun<leveled_setop.0.97347034>
10> F([[]]).
** exception error: no function clause matching leveled_setop:set_function(set_id) (/Users/thomas/Quviq/Customers/NHS/leveled/src/leveled_setop.erl, line 54)
in function leveled_setop:apply_setop/2 (/Users/thomas/Quviq/Customers/NHS/leveled/src/leveled_setop.erl, line 49)
Allow for return_keys of logical combinations of queries