scala - 为什么定界的延续原语名为 “shift”和 “reset”？

Question

我想我大致了解shift和reset的含义。但是我不明白为什么要这样命名？作为分隔连续原语的shift和reset与英语中的“shift”和“reset”单词有什么关系？

Answer 1

之所以这样称呼它们是因为它们的实现方式(通常)。

引用Direct Implementation of Shift and Reset in the MinCaml Compiler

By interpreting a program using the continuation semantics, we can regard the state of the program as a continuation stack. Then, reset can be thought of as marking the continuation stack, and shift capturing the continuation stack up to the nearest mark created by reset. Here is the overview of the implementation:

• When calling reset, set a reset mark to the stack
• When calling shift (fun k -> M), move a part of the stack frames up to the nearest reset mark to the heap
• When calling a continuation k, set a reset mark to the stack and copy the corresponding frames from the heap to the stack top.

A reset mark is inserted when k is called, because captured continuations are executed in an empty continuation.