> If you're adding in new information into the type system, you'd have to go through each part of the system that uses that type and update it to use the new information correctly.
It depends on what you do. If you (say) add a new field to an existing type, this will screw up pattern matching. It's a bit inconvenient, but typically not a big deal. On the other hand, if your previously non-nullable String field becomes a Maybe String, you're going to have to update every location where you access it... and that's exactly what a reasonable programmer wants to do. Unfortunately, you can't encode this in Javascript, so you're going to resort to 'grep' (good luck if you have the same field name for several objects), or forget about it and get runtime errors. Sure, in theory you can rely on your Javascript unit tests to detect the error, and you may be right in practice, or you may be out of luck.
Generally speaking, Haskell has its fair share of problems, but it's not one of them.
> If I start a project tomorrow in Haskell or Python, the GP's post is saying my Python project will be completed quicker but be less correct.
It definitely matches my own experience (it obviously depends on your proficiency in both languages, and Haskell will have only marginal advantages if you use String everywhere because types are hard).
> He is also saying that the amount of time I spend maintaining my Python project over the next few years will be higher than time spent maintain a same-feature Haskell project. There is absolutely zero evidence I have seen anywhere that this is correct and from experience it depends far more on the project itself and where the strengths of the language (and libraries!) lie than the language itself.
It's the kind of thing for which it is extremely hard to get any evidence for (and not only in Haskell vs Javascript debates), for obvious reasons. The best you can say is that the stronger guarantees of correctness offered by a strongly-typed program ensure that it makes it much easier to detect regressions. On the other hand, if, say, there are no third-party libraries for the problem domain at hand, strong typing will not magically fix that.
It depends on what you do. If you (say) add a new field to an existing type, this will screw up pattern matching. It's a bit inconvenient, but typically not a big deal. On the other hand, if your previously non-nullable String field becomes a Maybe String, you're going to have to update every location where you access it... and that's exactly what a reasonable programmer wants to do. Unfortunately, you can't encode this in Javascript, so you're going to resort to 'grep' (good luck if you have the same field name for several objects), or forget about it and get runtime errors. Sure, in theory you can rely on your Javascript unit tests to detect the error, and you may be right in practice, or you may be out of luck.
Generally speaking, Haskell has its fair share of problems, but it's not one of them.
> If I start a project tomorrow in Haskell or Python, the GP's post is saying my Python project will be completed quicker but be less correct.
It definitely matches my own experience (it obviously depends on your proficiency in both languages, and Haskell will have only marginal advantages if you use String everywhere because types are hard).
> He is also saying that the amount of time I spend maintaining my Python project over the next few years will be higher than time spent maintain a same-feature Haskell project. There is absolutely zero evidence I have seen anywhere that this is correct and from experience it depends far more on the project itself and where the strengths of the language (and libraries!) lie than the language itself.
It's the kind of thing for which it is extremely hard to get any evidence for (and not only in Haskell vs Javascript debates), for obvious reasons. The best you can say is that the stronger guarantees of correctness offered by a strongly-typed program ensure that it makes it much easier to detect regressions. On the other hand, if, say, there are no third-party libraries for the problem domain at hand, strong typing will not magically fix that.