Implement standard list operations

[vvergu]

Let's try to add the following standard list operations to DynSem:

• map L -map-> V or L -map(default)-> V
• zip: (L1, L2) -zip-> [(a, b), ...] or (L1, L2) -zip(default)-> [(a, b), ...]
• unzip [(A, B), ...] -unzip-> (L1, L2) or [(A, B), ...] -unzip(default)-> (L1, L2)

A possible approach for implementation is desugaring their uses to simple rules. Another approach is to add interpreter support for the operations.

[eelcovisser]

We need more standard operations on lists such as

• index: nth element of
• concat (++)

[vvergu]

Index we have. Use map access notation. We indeed need concat. Updating OP.

[vvergu]

Actually, concat is a different category of development. I've created #146 for it.