A "compound" object for Python like in ABC
Just throwing out an idea here. I want to consider the programming value of a Compound data type, such as found in the ABC programming language. I think it could considerably simplify Python in several different ways although it would require some significant changes. Crudely, a Compound is simply the ability to associate a label or key with an object -- flatly; i.e. in a "planar" dimension rather than a depth dimension like one might do with a variable name. We can denote a Compound with a (key:value) syntax, using a colon to signify the relationshiop. Compounds may collide when they are put into a Set (if their keys are the same). The default behavior can be like dict: overwrite the value -- but users can subclass the Compound data type and specify what to do. In the case of a Bag, it could __add__ the values; in the case of a database, it could throw an exception, etc. A Compound also has a __default__ value in the case of colliding with a non-compound type. For a countable Compound this would likely be 1. A dictionary becomes simply a set of Compounds; for example, {'a':1, 'b':2} is a *set* containing two Compound data elements. Nicely, this allows the empty set to have the normal syntax of "{}". Set would have to add the [] set/getitem syntax to deal with the common case of possible compound relationships among its members. It would return None if the item is not a Compound type otherwise it returns the compound's value. Additionally, set should NOT quietly ignore adding a duplicate element, they should collide and python's pre-defined collision behavior decides what happens. Creating a bag (or Counter) container now becomes very simple: make a Compound that run the add function for collisions. As another example, a Node (in a graph) is now simply "Node1":{"edge1", "edge2"} (a Compound) and a Graph simply a set of such Compounds. Some other possibilities: the Compound is a special data type that exist in the border between an atom and a collection. The Compound's constructor can exploit this. If a collection is passed as the first paramater to the compound's constructor, all sorts of things can be done. Compound(myset, 1) could return a dictionary with all values set to 1. Given a list instead, it could return an enumeration. This is all rather sloppy, but I wanted to put it out here to see what kind of interest there might be.... Mark
participants (2)
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David Townshend -
Mark Janssen