stdlib

Try

• Try.map[B](f: A => B): transform successful values
• Try.flatMap[B](f: A => Try[B]): tries to transform successful values
• Try.recover[B](f: PartialFunction[Throwable, A]): Try[B]: transforms some failures to successes
• Try.recover[B](f: PartialFunction[Throwable, Try[A]]): Try[B]: tries to transforms some failures to successes

Future

• map and flatMap evaluate after a future value is resolved
• zip and traverse join together multiple Futures into a single Future and evaluated in parallel
• recover and recoverWith handle failures

Tips and Tricks

• Use foldLeft to do computation based on an optional value
• Use Either.fold(identity, identity) to return whichever of the Left or Right value is present, provided both are of the same type
• When to use List, cats.data.Chain or Vector
• BP Use List as default, IterableOnce as parameter and then call to get an Iterator

foldLeft and foldRight

• intuition
• applies to lists or sequences that can be thought as consisting of Cons and Nil
• foldRight is constructor substitution, replacing Cons and Nil with different functions
  • is lazy, looking at each element as needed
  • works on infinite sequences
  • obeys associativity but the order isn't guaranteed, specifically, does not imply that it works from right to left
• foldLeft is loop replacement
  • is strict, looping through all elements