Dependent Types for F#

Re:Dependent Types for F# by HumanDrivenDev on Tuesday December 05, 2017 @03:21PM (#15855425)

Right. I said dependent types would allow you to statically declare integer ranges, as is my understanding.

It's interesting to me how Ada takes the approach of blending types and run time contracts. In most languages it would be two different things - a function that takes int, then a contract or assert that handles the value.

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Re:Dependent Types for F# by mjn on Tuesday December 05, 2017 @04:03PM (#15855942)

Some Lisp implementations (like SBCL) also do that blending, although they can statically catch some integer range violations too. For example if you declare a variable to be an (integer 50 100) and try to assign a literal 30 to it, you'll get a compile-time warning in SBCL:

    ;   Constant 30 conflicts with its asserted type (INTEGER 50 100).

But in many other cases it'll generate a runtime check instead, because the static type checking is basically best-effort.

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Re:Dependent Types for F# by DonaldFisk on Tuesday December 05, 2017 @03:35PM (#15855570)

They allow you to statically declare integer ranges (as well as other things), even if their bounds are unknown until run-time, and without requiring a run-time type check.

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