Ask General Programming Questions Not Worth Their Own Thread

The Something Awful Forums > Discussion > Serious Hardware/Software Crap > The Cavern of COBOL > Ask General Programming Questions Not Worth Their Own Thread

Save the whales: Aug 31, 2004; by T. Finn

I'll state my question using Java terminology, but I'm curious as to whether there's a general name for this kind of data structure.

Recently I came upon the need for a data structure that is a bit of a cross between a Map and a Set. I ended up calling it BinaryRelation<L, R>. Its most important methods are:

code:

/*
pairs the given left-hand and right-hand values
*/
void put(L left, R right);

/*
returns a collection view of the left-hand values paired with the specified right-hand value
*/
Collection<L> getLeft(R right);

/*
returns a collection view of the right-hand values paired with the specified left-hand value
*/
Collection<R> getRight(L left);

It's kind of like a bidirectional map in that you can find associated values for keys or associated keys for values, but it's different in that neither keys nor values must be unique - only key-value pairs must be unique.

I've already written the Java code to implement this, so I'm not asking how it can be done, but I'm curious - is there a general name for this kind of data structure? Has it been implemented in any popular programming languages or libraries? I wasn't able to find anything like this after a bit of Googling and I was surprised because it seems like such a useful way of describing a relation between two sets of objects. I know for certain I'm going to use it in every web application I make from here on out.

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The Something Awful Forums > Discussion > Serious Hardware/Software Crap > The Cavern of COBOL > Ask General Programming Questions Not Worth Their Own Thread