Why does queue have front but priority queue has top in stl?

Question

Both are container adaptors and both are defined in the header <queue> still they both have different interfaces to access the 'first' element. I can understand the lack of a back due to the constraints of the data structure but naming front differently confuses me.

Answer 1

The priority_queue container adaptor is a convenience wrapper for the standard library's heap algorithms, using a sequence container as a classic binary heap. The name top likely reflects this association; we speak of the "top" of a heap, since we visualize it as a heap-ordered binary tree, with the element of greatest priority at the root (top).