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I have written books on Common Lisp and Scheme. Their power feature to me is the combination of functional programming (functions without side effects) and how

I have written books on Common Lisp and Scheme. Their power feature to me is the combination of functional programming (functions without side effects) and how these small functions can be built bottom-up in an interactive repl. Other languages like Python and Ruby also support repl style development, but aren't sufficiently functional. A little off topic, but I am working on a commercial product (KGcreator, a tool for generating graph data for knowledge graphs) and started prototyping in both Racket and Haskell. It was a tough call but I chose Haskell. I think of Haskell as being another Lisp language that also supports repl style development.

soapdog 7y ago
Tell us more about your books. I'm addicted to scheme books :-) Also, what made you choose Haskell for your project? Can you share some of the reasoning?
- deepaksurti 7y ago
  See Mark’s books here [1] [1]: http://markwatson.com/books/ http://markwatson.com/books/
- mark_l_watson 7y ago
  I think the deployment story for Haskell is better than Racket. It is easy enough make standalone Racket executables but with stack and cabal it is baked in to easily build multiple executables, separate libraries, keep everything tidy. Racket is much better to get something done and working quickly. Same comment for Common Lisp. Haskell has great support for strongly types web services (servant) and lots of great libraries. Racket has a very rich ecosystem of libraries, custom languages (like Typed Racket). Both are great. EDIT: It takes me longer to get to working code in Haskell but once written the code has higher value to me because it is so much faster/easier to refactor, change APIs, reuse in other projects, etc. I just did a major refactoring/code-tidying this morning, and it was very simple to do.
xfer 7y ago
> functional programming (functions without side effects) CL has mutable data structures(lists are mutable by default) and setf etc. Scheme/Clojure makes a much pleasant functional programming without side effects experience.
- fiddlerwoaroof 7y ago
  RxRS Scheme has mutable conses as well. One of the reasons Racket isn’t called MzScheme anymore is that its primitive conses are immutable (iirc)
  - darkpuma 7y ago
    Immutable cons cells also lets Racket implement a constant time `list?`, which is kind of nice. https://docs.racket-lang.org/reference/pairs.html?q=list?#%28def._%28%28quote._~23~25kernel%29._list~3f%29%29 https://docs.racket-lang.org/reference/pairs.html?q=list?#%2...
    - fiddlerwoaroof 7y ago
      This doesn’t require immutable conses if you just update the cache whenever the cdr is mutated.
      - darkpuma 7y ago
        If the last cdr in a list is modified, then you need to propagate that change up to the front of the list during that modification, or check the whole list when you run `list?`. Either way, you pay linear time for it.
        fiddlerwoaroof 7y ago
        Only if the new value makes it no longer a list (or changes a dotted list into a real list). My hunch is that this would, in normal usages, work out to constant time (setf (cdr foo) ...) with the occasional (setf (cdr foo) atom) requiring the change in state to be propagated in linear time.
momentoftop 7y ago
I love Haskell, but as far as GHC goes, its REPL story is awful: your environment doesn't even survive loading a new file! You can ask it to replay your bindings, but that's a pretty crappy solution, likely to produce unpredictable errors and, if you're doing any serious computation (such as when theorem proving), it's probably useless. Compare this to a language like Ocaml, where I have worked at the exact same REPL, modifying the same environment, for months at a time. This was such a standard thing to do in the Lisp and ML worlds that these languages traditionally include a save-lisp-and-die function which saves your entire runtime to disk so it can be reloaded later. (We used DMTCP in Ocaml for the same effect). Not to moan too much. Haskell is still my favourite language. I just wish it had a decent REPL.
- schwurb 7y ago
  Isn't the lack of a stateful REPL a feature in Haskell? Don't get my wrong, I love image/state-based developing (having working knowledge with SmallTalk and just getting into emacs). But I think it is quite haskelly to introduce functions that create the state rather than create the state interactively yourself. This should be good for mocking and tests also. Yes, this is more work than in most other practical languages, but this is Haskell for you ;)

soapdog 7y ago

Tell us more about your books. I'm addicted to scheme books :-) Also, what made you choose Haskell for your project? Can you share some of the reasoning?

deepaksurti 7y ago
See Mark’s books here [1] [1]: http://markwatson.com/books/ http://markwatson.com/books/
mark_l_watson 7y ago
I think the deployment story for Haskell is better than Racket. It is easy enough make standalone Racket executables but with stack and cabal it is baked in to easily build multiple executables, separate libraries, keep everything tidy. Racket is much better to get something done and working quickly. Same comment for Common Lisp. Haskell has great support for strongly types web services (servant) and lots of great libraries. Racket has a very rich ecosystem of libraries, custom languages (like Typed Racket). Both are great. EDIT: It takes me longer to get to working code in Haskell but once written the code has higher value to me because it is so much faster/easier to refactor, change APIs, reuse in other projects, etc. I just did a major refactoring/code-tidying this morning, and it was very simple to do.

xfer 7y ago

> functional programming (functions without side effects) CL has mutable data structures(lists are mutable by default) and setf etc. Scheme/Clojure makes a much pleasant functional programming without side effects experience.

fiddlerwoaroof 7y ago
RxRS Scheme has mutable conses as well. One of the reasons Racket isn’t called MzScheme anymore is that its primitive conses are immutable (iirc)
- darkpuma 7y ago
  Immutable cons cells also lets Racket implement a constant time `list?`, which is kind of nice. https://docs.racket-lang.org/reference/pairs.html?q=list?#%28def._%28%28quote._~23~25kernel%29._list~3f%29%29 https://docs.racket-lang.org/reference/pairs.html?q=list?#%2...
  - fiddlerwoaroof 7y ago
    This doesn’t require immutable conses if you just update the cache whenever the cdr is mutated.
    - darkpuma 7y ago
      If the last cdr in a list is modified, then you need to propagate that change up to the front of the list during that modification, or check the whole list when you run `list?`. Either way, you pay linear time for it.
      - fiddlerwoaroof 7y ago
        Only if the new value makes it no longer a list (or changes a dotted list into a real list). My hunch is that this would, in normal usages, work out to constant time (setf (cdr foo) ...) with the occasional (setf (cdr foo) atom) requiring the change in state to be propagated in linear time.

momentoftop 7y ago

I love Haskell, but as far as GHC goes, its REPL story is awful: your environment doesn't even survive loading a new file! You can ask it to replay your bindings, but that's a pretty crappy solution, likely to produce unpredictable errors and, if you're doing any serious computation (such as when theorem proving), it's probably useless. Compare this to a language like Ocaml, where I have worked at the exact same REPL, modifying the same environment, for months at a time. This was such a standard thing to do in the Lisp and ML worlds that these languages traditionally include a save-lisp-and-die function which saves your entire runtime to disk so it can be reloaded later. (We used DMTCP in Ocaml for the same effect). Not to moan too much. Haskell is still my favourite language. I just wish it had a decent REPL.

schwurb 7y ago
Isn't the lack of a stateful REPL a feature in Haskell? Don't get my wrong, I love image/state-based developing (having working knowledge with SmallTalk and just getting into emacs). But I think it is quite haskelly to introduce functions that create the state rather than create the state interactively yourself. This should be good for mocking and tests also. Yes, this is more work than in most other practical languages, but this is Haskell for you ;)