Re: language design implications for variant records in a pascal-like language

Gene <gene.ressler@gmail.com> writes:


> True.


Not clear what you're replying to.


> Much nicer would be
>
> type Possibly_Valid_Float is new Float with (Unknown);


OK, but you can't expect existing code that uses Float to
work properly with Possibly_Valid_Floats.


Also, you can't have Possibly_Valid_Floats other than those
two possibilities -- it's either a Float or it's not.


You can do this sort of thing in OCaml. Type "Maybe(Float)" is either
a float or nothing. It's pretty elegant, and doesn't require any
special "enumeration types" or "enumeration type extensions".


- Bob

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