9 ms·

well played. I think that just got added to my standard vocabulary. Caching has caused more errors and bugs that I've had to deal with than I can recall. My fav

well played. I think that just got added to my standard vocabulary. Caching has caused more errors and bugs that I've had to deal with than I can recall. My favorite was an off by one error where we returned nicely cached info -- just for the previous user who came through our system! :facepalm: That was a bad one.

taf2 6y ago
Yeah but the speed.
saganus 6y ago
Here goes the obligatory > There are only two hard things in Computer Science...
- jholman 6y ago
  I can never remember what they are, though. To avoid this problem, I think I wrote them down on a post-it, but I had too many post-its on my desk so I got rid of them all, and now I can't remember.
  - joubert 6y ago
    > wrote them down on a post-it You write it on local media and kept it on-premises? Cloud is the new thing, I hear.
    - ampdepolymerase 6y ago
      The Post-it was but a cache.
      - mrathys 6y ago
        I would consider the Post-it as persistent storage or the backup. Your memory would be the cache :D
  - llarsson 6y ago
    The two most difficult ones are naming things, cache invalidation, and off-by-one errors. HTH. ;)
    - samb1729 6y ago
      What does HTH mean?
      - sgn 6y ago
        Hope That Help, HTH.
        kzrdude 6y ago
        "Hope this helps" I see it with HAND "have a nice day" too
        _puk 6y ago
        I've always read it as "Happy To Help". I see that's wrong, but ignorance has made the internet seem just that little bit warmer all these years!
        gwd 6y ago
        I think it could probably mean "Happy to help" if said in response to a thanks of some sort. Saying it before someone has said thanks is a bit presumptuous. :-)
      - mattacular 6y ago
        "Hope this helps" (sometimes used sarcastically)
    - zaphirplane 6y ago
      They are likely making a joke about caching the answer
    - Xelbair 6y ago
  - bryanrasmussen 6y ago
    this reminds me I was dumpster diving at a place with lots of post-it notes and there was one that said 2HCS => whatchamacallit, CI! what that you? on edit: I'm going to let that 'what that you' stand because one of the hardest things about HN posts is grammatical correctitude.
- deleted 6y ago
  [deleted]
anyfoo 6y ago
That's because essentially, "state" and "caching" are the same thing on some level. And the problem with state is that you have to make sure all your state transitions don't cause bugs. What we know as a "cache" is essentially creating new state representing existing state, with all new transitions...
- bin_bash 6y ago
  Cache is a type of state but not necessarily the other way around
  - anyfoo 6y ago
    In the efficient implementation of a pure functional language (say Haskell without MVars), what really is the difference between state and cache? I know this is overly philosophical, and in practical scenarios we readily (although not always unambiguously) differentiate between "cache" and "state", but the point about transitions and that being a major source of bugs still stands.
    - eru 6y ago
      > In the efficient implementation of a pure functional language (say Haskell without MVars), what really is the difference between state and cache? If you want to unify state and cache, you might want to go down a different route: Think of log based filesystems (or a log based data base). Instead of defining your operations in terms of state, you define them as pure functions of the log. So your log is full of operations. Writing just means appending a symbolic operation like `write(key, value)` to your log. And you define the result of `read(key)`: scan backwards through the log until you hit the last instance of `write(x, value)` and the return that `value`. Now state means: compact your log by replacing a swath of `write` log entries with one big `snapshot` operation that encompasses many key/value pairs. Alternatively, you can also define state to mean caching your `read` operations. In this approach, it's no coincidence that the log is a data structure that has a linear shape: the evolution of state over time is also linear. (With some cleverness you can replace the linear structure with eg a DAG; and then also think about how you merge divergent states.)

taf2 6y ago

Yeah but the speed.

saganus 6y ago

Here goes the obligatory > There are only two hard things in Computer Science...

jholman 6y ago
I can never remember what they are, though. To avoid this problem, I think I wrote them down on a post-it, but I had too many post-its on my desk so I got rid of them all, and now I can't remember.
- joubert 6y ago
  > wrote them down on a post-it You write it on local media and kept it on-premises? Cloud is the new thing, I hear.
  - ampdepolymerase 6y ago
    The Post-it was but a cache.
    - mrathys 6y ago
      I would consider the Post-it as persistent storage or the backup. Your memory would be the cache :D
- llarsson 6y ago
  The two most difficult ones are naming things, cache invalidation, and off-by-one errors. HTH. ;)
  - samb1729 6y ago
    What does HTH mean?
    - sgn 6y ago
      Hope That Help, HTH.
      - kzrdude 6y ago
        "Hope this helps" I see it with HAND "have a nice day" too
        _puk 6y ago
        I've always read it as "Happy To Help". I see that's wrong, but ignorance has made the internet seem just that little bit warmer all these years!
        gwd 6y ago
        I think it could probably mean "Happy to help" if said in response to a thanks of some sort. Saying it before someone has said thanks is a bit presumptuous. :-)
    - mattacular 6y ago
      "Hope this helps" (sometimes used sarcastically)
  - zaphirplane 6y ago
    They are likely making a joke about caching the answer
  - Xelbair 6y ago
- bryanrasmussen 6y ago
  this reminds me I was dumpster diving at a place with lots of post-it notes and there was one that said 2HCS => whatchamacallit, CI! what that you? on edit: I'm going to let that 'what that you' stand because one of the hardest things about HN posts is grammatical correctitude.
deleted 6y ago
[deleted]

anyfoo 6y ago

That's because essentially, "state" and "caching" are the same thing on some level. And the problem with state is that you have to make sure all your state transitions don't cause bugs. What we know as a "cache" is essentially creating new state representing existing state, with all new transitions...

bin_bash 6y ago
Cache is a type of state but not necessarily the other way around
- anyfoo 6y ago
  In the efficient implementation of a pure functional language (say Haskell without MVars), what really is the difference between state and cache? I know this is overly philosophical, and in practical scenarios we readily (although not always unambiguously) differentiate between "cache" and "state", but the point about transitions and that being a major source of bugs still stands.
  - eru 6y ago
    > In the efficient implementation of a pure functional language (say Haskell without MVars), what really is the difference between state and cache? If you want to unify state and cache, you might want to go down a different route: Think of log based filesystems (or a log based data base). Instead of defining your operations in terms of state, you define them as pure functions of the log. So your log is full of operations. Writing just means appending a symbolic operation like `write(key, value)` to your log. And you define the result of `read(key)`: scan backwards through the log until you hit the last instance of `write(x, value)` and the return that `value`. Now state means: compact your log by replacing a swath of `write` log entries with one big `snapshot` operation that encompasses many key/value pairs. Alternatively, you can also define state to mean caching your `read` operations. In this approach, it's no coincidence that the log is a data structure that has a linear shape: the evolution of state over time is also linear. (With some cleverness you can replace the linear structure with eg a DAG; and then also think about how you merge divergent states.)