Thoughts on Rust, a few thousand lines in

Re:Thoughts on Rust, a few thousand lines in by Misdicorl on Wednesday January 09, 2019 @05:31PM (#18869681)

I believe the way this is solved is by having the type of escaped(foo) different than that of parse(foo) and only accepting a EscapedString in doBaz and an ParsedString in doBar.

Your type structure at no extra runtime cost is String : ParsedString : EscapedString.

This ensures you don't escape strings before parsing them too. Nice!

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Re:Thoughts on Rust, a few thousand lines in by afraca on Thursday January 10, 2019 @03:49AM (#18872468)

This is common in Haskell as well using `newtype`. You can have type aliases like

  type A = B

but you can use the following function with a B:

  f :: A -> _

whereas

  newtype EscapedString = EscapedString String
  f' :: EscapedString -> _

would prevent from using f' with the wrong data. Newtype is a zero-cost abstraction.

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