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There is one aspect to this debate that is worth pointing out. What about generative testing, which is possible in static or dynamically typed languages? The ar

There is one aspect to this debate that is worth pointing out. What about generative testing, which is possible in static or dynamically typed languages? The article mentions that testing is perhaps more important in a dynamically typed language since there is less compiler support. But for example, Clojure rolled out the very clever Clojure.spec library that allows you to precisely specify all details relating to function arguments, data structures, etc, in even more fine-tuned methodology than just types; you can specify that the second argument to a function must be larger than the first, or that a function should only return a value between 5 and 10, etc. These "specs" have the interesting property of being run-time checked or compile-time checked in the form of automatic tests, which can generate inputs based on the specs. In such a case, the line between these two type environments narrows.

yawaramin 9y ago
Clojure.spec is very clever, but it can be exactly duplicated in a statically-typed language by unit or property testing. It doesn't bring anything to the table that is totally a superset of static typing. > In such a case, the line between these two type environments narrows. Not really. Static types still offer you total proofs of the properties you encode as types, not just experimental results of tests.
- hellofunk 9y ago
  Generative testing is just one application of Clojure.spec. It does more than just aid in testing. It doubles as a runtime contract system, a data coercion system, and some folks are using it for compile-time checks as well (not in the testing sense, though I haven't read up on how they are doing that). It is not a proof-like system, but outside of dependent typing, static typing does not catch value-related bugs, but Clojure.spec can. In a static type system, how easily would it be to exactly specify and guarantee that a function's second parameter is of a higher value than its first, or that a function's output is an integer between 5 and 50, etc? Clojure.spec is just predicate functions composed together to define the flow of data in a program, and those compositions can be used in a variety of ways.
  - yawaramin 9y ago
    > ... static typing does not catch value-related bugs, but Clojure.spec can. Can you provide an example? > In a static type system, how easily would it be to exactly specify and guarantee that a function's second parameter is of a higher value than its first, or that a function's output is an integer between 5 and 50, etc? Scala: def foo(param1: Int, param2: Int): Int = { require(param2 > param1, "Param2 must > param1") param2 - param1 ensuring { result => result >= 5 && result <= 50 } }

yawaramin 9y ago

Clojure.spec is very clever, but it can be exactly duplicated in a statically-typed language by unit or property testing. It doesn't bring anything to the table that is totally a superset of static typing. > In such a case, the line between these two type environments narrows. Not really. Static types still offer you total proofs of the properties you encode as types, not just experimental results of tests.

hellofunk 9y ago
Generative testing is just one application of Clojure.spec. It does more than just aid in testing. It doubles as a runtime contract system, a data coercion system, and some folks are using it for compile-time checks as well (not in the testing sense, though I haven't read up on how they are doing that). It is not a proof-like system, but outside of dependent typing, static typing does not catch value-related bugs, but Clojure.spec can. In a static type system, how easily would it be to exactly specify and guarantee that a function's second parameter is of a higher value than its first, or that a function's output is an integer between 5 and 50, etc? Clojure.spec is just predicate functions composed together to define the flow of data in a program, and those compositions can be used in a variety of ways.
- yawaramin 9y ago
  > ... static typing does not catch value-related bugs, but Clojure.spec can. Can you provide an example? > In a static type system, how easily would it be to exactly specify and guarantee that a function's second parameter is of a higher value than its first, or that a function's output is an integer between 5 and 50, etc? Scala: def foo(param1: Int, param2: Int): Int = { require(param2 > param1, "Param2 must > param1") param2 - param1 ensuring { result => result >= 5 && result <= 50 } }