History (programming language)

Not to be confused with Timeline of esoteric programming languages.

History is a joke programming language invented by User:A that depends on the History data structure, an esoteric data structure inspired by queues that cannot delete anything.

The History data structure

Its behavior is very simplar to a queue. There are 2 primary operations: UPDATE, and INSERT.

The following table explains them, and shows how to implement them in History.

op	meaning
UPDATE X	Update the current number as X, and put the previous "current number" into history.
INSERT X	Insert the backmost item to the index between index X and index X+1 without deleting the backmost item.
TOP X	Insert the top item to the index between X and X+1 without deleting the item.
ONSERT X	Put position X onto the top of the history without deleting the item.

An example session of History

HISTORY:
COMMAND: UPDATE 1
HISTORY:
    @UPDATE #1 is 1
COMMAND: UPDATE 2
HISTORY:
    @UPDATE #2 is 2
    @UPDATE #1 is 1
COMMAND: INSERT 2
HISTORY:
    @UPDATE #3 is 1
    @UPDATE #2 is 2
    @UPDATE #1 is 1
COMMAND: BYE

Computational class

It is not Turing-complete, of course. (It cannot execute an infinite loop, or even any sort of conditional statement.)