Circular Buffer in Erlang
A data structure that uses a single, fixed-size buffer as if it were connected end-to-end.
exercism fetch erlang circular-buffer
A circular buffer, cyclic buffer or ring buffer is a data structure that uses a single, fixed-size buffer as if it were connected end-to-end.
A circular buffer first starts empty and of some predefined length. For example, this is a 7-element buffer:
[ ][ ][ ][ ][ ][ ][ ]
Assume that a 1 is written into the middle of the buffer (exact starting location does not matter in a circular buffer):
[ ][ ][ ][ ][ ][ ]
Then assume that two more elements are added — 2 & 3 — which get appended after the 1:
[ ][ ][ ][ ]
If two elements are then removed from the buffer, the oldest values inside the buffer are removed. The two elements removed, in this case, are 1 & 2, leaving the buffer with just a 3:
[ ][ ][ ][ ][ ][ ]
If the buffer has 7 elements then it is completely full:
When the buffer is full an error will be raised, alerting the client that further writes are blocked until a slot becomes free.
The client can opt to overwrite the oldest data with a forced write. In this case, two more elements — A & B — are added and they overwrite the 3 & 4:
Finally, if two elements are now removed then what would be returned is not 3 & 4 but 5 & 6 because A & B overwrote the 3 & the 4 yielding the buffer with:
[ ][A][B][ ]
In order to run the tests, issue the following command from the exercise directory:
For running the tests provided,
rebar3 is used as it is the official build and
dependency management tool for erlang now. Please refer to the tracks installation
instructions on how to do that.
In order to run the tests, you can issue the following command from the exercise directory.
$ rebar3 eunit
Each problem defines a macro
TEST_VERSION in the test file and
verifies that the solution defines and exports a function
returning that same value.
To make tests pass, add the following to your solution:
The benefit of this is that reviewers can see against which test version an iteration was written if, for example, a previously posted solution does not solve the current problem or passes current tests.
For detailed information about the Erlang track, please refer to the help page on the Exercism site. This covers the basic information on setting up the development environment expected by the exercises.
Submitting Incomplete Solutions
It's possible to submit an incomplete solution so you can see how others have completed the exercise.