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by lolinder 2489 days ago
Does "if it compiles it's bug free" actually work in practice? I've heard a lot of advocates for Haskell and Rust use similar lines to this, but it seems to me like it can only be true for a limited subset of all bugs. Elm's "no runtime errors in production" claim has a more reasonable-sounding scope.
3 comments
fsloth 2489 days ago
Sure, it's limited to a subset of all bugs but with a proper typesystem the category of bugs you can remove from code by just encoding the semantics and algebra into the types is quite large.

So if you know how to formulate the problem so it leans heavily on the type system, you can implement something like a binary tree container, and presume it is correct when it compiles.

Following the same parameters bestows rest of the codebase with this robustness.

See for example the ACM article "Ocaml for the masses" by Yaron Minsky of Jane Street for very lucid practical examples https://queue.acm.org/detail.cfm?id=2038036

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FullyFunctional 2488 days ago
"It doesn't eliminate bugs, but the bugs that remain are better bugs".

Better bugs in this context is bugs at a higher level, eg. application logic issues.

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fsloth 2489 days ago
... to be fair, it takes a bit getting used to a compiler that is as strict, but, when you learn how you need to implement various things, it increases your velocity since you can type stuff and not bother with too much intermediary testing because you can trust you've pretty much typed as you meant.
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