?CURSOR/NEXT

Sets the cursor at the next key value

Input stack: cursor

Output stack: [key value] or []

If there is a next key/value pair in the database, [key value] will be pushed onto the stack. Otherwise, [] will be pushed. Useful in conjunction with UNWRAP, SOME? and NONE?.

PumpkinDB> ["1" "2" ASSOC "2" "2" ASSOC COMMIT] WRITE [CURSOR 'c SET c ?CURSOR/FIRST DROP c CURSOR/NEXT] READ UNWRAP
"2" "2"

Allocation

Allocates for values to be put onto the stack

Errors

NoTransaction error if there's no current write transaction

InvalidValue error if the cursor identifier is incorrect or expired

Tests

works : ["1" "2" ASSOC "2" "2" ASSOC COMMIT] WRITE [CURSOR 'c SET c ?CURSOR/FIRST DROP c ?CURSOR/NEXT] READ ["2" "2"] EQUAL?.
requires_txn : ["1" ?CURSOR/NEXT] TRY UNWRAP 0x08 EQUAL?.
empty_stack : [?CURSOR/NEXT] TRY UNWRAP 0x04 EQUAL?.
invalid_cursor : [["1" ?CURSOR/NEXT] READ] TRY UNWRAP 0x03 EQUAL?.

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