Evaluation in Cats: the Good, the Bad, and the Lazy
summary
Cats’ Eval provides a concrete way to encode evaluation strategies into types, offering now/always/later semantics that map to eager, repeated, and call‑by‑need behavior; it includes a defer and trampoline mechanism that lets recursive algorithms avoid stack overflow (demonstrated by a counter example where map alone still recurses but defer protects the stack). Examples show that mapping/flatMapping stays lazy, that calling .value defeats laziness, and that Eval underpins streaming, Foldable and lazy/infinite data structures.
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