merging two dictionaries

[Skaperen]

i created a thing in C in 2 layers called avlmap.  the lower layer was more like a mechanism to manage an AVL tree (caller provides comparison functions, worked with pointers, inserting nodes, etc).  the upper layer was more abstract, which is not much in C (caller worked with key:value pairs, inserting keys, assigning values, while the library managed a cursor that tracked key position).  the upper layer had a separate insert function for duplicate keys.  duplicates were actually real nodes in the AVL tree, other functions dealt with duplicates with no issues.  searching a key that had duplicates would get the first of them (the first in order of insertion).  doing a position move forward would get the next key.  doing a position move back would go back to the first key.  moving forward until the key changes and moving back one would be at the last of the duplicate keys.  without keys and with just values it worked like a list.  with just keys and without values it worked like a set.  an assembly language version of it for IBM mainframes was written a few years before (all my mainframe code was lost). you can get the C source as a tarball compressed by gzip, bzip2, or xz.