4 ms·

I think the better analogy is: all the parts are brightly colored, and if you try to put a red part in a blue hole the compiler won't let you. Okay I guess that

I think the better analogy is: all the parts are brightly colored, and if you try to put a red part in a blue hole the compiler won't let you. Okay I guess that's not really an analogy anymore, but, you get the point.

taeric 13y ago
Same basic analogy, though. If the parts come such that they only fit together one way, then finding how to get them together can be deduced by looking at them. Falls flat when either a) you don't fully understand the parts or b) you are wanting to try a combination not strictly accounted for in the designing of the existing parts. Problem A is straight forward. Having an in depth knowledge of the "types" in a system has clear benefits. However, not really understanding the types is doable, provided you are strictly in the "assembly" phase of development. I believe that is what this post was about. Problem B is the killer to me. Often "combinations not accounted for" include partial combinations. It is not unreasonable to want to make sure the wheels of a bike spin with the chain before the pedals are placed.
- nbouscal 13y ago
  Have you played with Haskell at all? Partial combinations aren't a problem. Partial application is extremely well-supported. The goal of a type system is that the only combinations that don't work are broken combinations. Haskell isn't all the way there yet (imho dependent types will be necessary), but it's very close, and more than close enough for 99.9% of real work. Completely agree on your assessment of problem A, and that that's what this post is about. Learning the actual math behind the constructions is definitely beneficial, but for people who don't have the time or inclination to do that, this post demonstrates that they can still get enough of the benefits to be productive.
  - taeric 13y ago
    I confused things by using terminology here. I did not mean partial as in "partial application." I mean partial as in "isn't fully built." Consider, a bike that doesn't have pedals or even all spokes is a broken combination. You can still spin the parts that are assembled and see what will happen, though. So, unless I am wrong on this, point B is still troublesome to me. There is also a concern on whether the "assembly" phase is where time is best saved. How much more effort did it take for some elements so that they would have these "easily assembled" types?
    - nbouscal 13y ago
      The assembly optimizations come for free, in a sense, because what is really being optimized with the extra work is composability. Assembly time isn't all that important, but composability is absolutely essential. Regarding things that aren't fully built, I really would need an example to be able to comment. I think the analogy has reached the limit of its usefulness :)
      - taeric 13y ago
        I think my point is best summed up by saying that I can still run a project that has failing unit tests. To my knowledge, I can not run a program that fails type checking. The argument for this is typically "once it typechecks, it works." However, sometimes I can see enough from the output of a non-test passing piece of code to know whether the idea is even sound.
        nbouscal 13y ago
        I think the only reason you think not being able to run a program that doesn't type check is a problem is because you are used to a workflow in which running a program is how you test your ideas. The workflow used to explore ideas while programming in a strongly typed language is of course very different. Personally I think it's a lot better, but that's just opinion.
        taeric 13y ago
        That is an amusing personal attack. :) I test my ideas by executing them, yes. Are you truly claiming that you have all of your ideas completely fleshed out before you test any of them? That sounds incredibly impressive, if so. Can it be done in some cases? Almost certainly. I question whether it can in all, though. Even most.
        mightybyte 13y ago
        You don't have to have them completely fleshed out. But you do have to have them fleshed out to the type level. The Haskell compiler can be an invaluable aid in fleshing out the design of problems. Especially when they are complex difficult to wrap your head around.

taeric 13y ago

Same basic analogy, though. If the parts come such that they only fit together one way, then finding how to get them together can be deduced by looking at them. Falls flat when either a) you don't fully understand the parts or b) you are wanting to try a combination not strictly accounted for in the designing of the existing parts. Problem A is straight forward. Having an in depth knowledge of the "types" in a system has clear benefits. However, not really understanding the types is doable, provided you are strictly in the "assembly" phase of development. I believe that is what this post was about. Problem B is the killer to me. Often "combinations not accounted for" include partial combinations. It is not unreasonable to want to make sure the wheels of a bike spin with the chain before the pedals are placed.

nbouscal 13y ago
Have you played with Haskell at all? Partial combinations aren't a problem. Partial application is extremely well-supported. The goal of a type system is that the only combinations that don't work are broken combinations. Haskell isn't all the way there yet (imho dependent types will be necessary), but it's very close, and more than close enough for 99.9% of real work. Completely agree on your assessment of problem A, and that that's what this post is about. Learning the actual math behind the constructions is definitely beneficial, but for people who don't have the time or inclination to do that, this post demonstrates that they can still get enough of the benefits to be productive.
- taeric 13y ago
  I confused things by using terminology here. I did not mean partial as in "partial application." I mean partial as in "isn't fully built." Consider, a bike that doesn't have pedals or even all spokes is a broken combination. You can still spin the parts that are assembled and see what will happen, though. So, unless I am wrong on this, point B is still troublesome to me. There is also a concern on whether the "assembly" phase is where time is best saved. How much more effort did it take for some elements so that they would have these "easily assembled" types?
  - nbouscal 13y ago
    The assembly optimizations come for free, in a sense, because what is really being optimized with the extra work is composability. Assembly time isn't all that important, but composability is absolutely essential. Regarding things that aren't fully built, I really would need an example to be able to comment. I think the analogy has reached the limit of its usefulness :)
    - taeric 13y ago
      I think my point is best summed up by saying that I can still run a project that has failing unit tests. To my knowledge, I can not run a program that fails type checking. The argument for this is typically "once it typechecks, it works." However, sometimes I can see enough from the output of a non-test passing piece of code to know whether the idea is even sound.
      - nbouscal 13y ago
        I think the only reason you think not being able to run a program that doesn't type check is a problem is because you are used to a workflow in which running a program is how you test your ideas. The workflow used to explore ideas while programming in a strongly typed language is of course very different. Personally I think it's a lot better, but that's just opinion.
        taeric 13y ago
        That is an amusing personal attack. :) I test my ideas by executing them, yes. Are you truly claiming that you have all of your ideas completely fleshed out before you test any of them? That sounds incredibly impressive, if so. Can it be done in some cases? Almost certainly. I question whether it can in all, though. Even most.
        mightybyte 13y ago
        You don't have to have them completely fleshed out. But you do have to have them fleshed out to the type level. The Haskell compiler can be an invaluable aid in fleshing out the design of problems. Especially when they are complex difficult to wrap your head around.