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A comment on Introduction to Functional Programming in OCaml. Parent comment

Re:Introduction to Functional Programming in OCaml by agumonkey on Thursday August 23, 2018 @10:22AM (#17827467)
about 2, I remember some old lisp book (Queinnec L.I.S.P) said that if mutable state is entirely contained and invisible, you can forget about purity.

It's cool that cpp is 'flattening' through fp idioms, you can avoid its complexity without leaving the country entirely.

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Re:Introduction to Functional Programming in OCaml by kazinator on Thursday August 23, 2018 @10:42AM (#17827653)
E.g. a pure function can work internally by mutating some local variables. Locally constructed new objects such as conses can be mutated before being returned to the caller. Blackbox testing cannot tell.
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