Enumerations

[Shea Levy]

Hello,

Is it possible to declare an enumeration of a given size, whose enumerators are not necessarily sequential from 0 to the top? For example, can I declare an enumeration Foo the size of an int, whose only valid values are Bar, Baz, and Qux, where Bar is represented by 1, Baz by 30, and Qux by 16?

Thanks,
Shea

[gmhwxi]

How about the following approach:

abst@ype Foo = int
macdef Bar = $extval (Foo, "1")
macdef Baz = $extval (Foo, "30")
macdef Quz = $extval (Foo, "16")

[Shea Levy]

Ah, yes that will do. Followup question: is it possible to use Foo in existentials/constraints? Can I for example write a function that takes any Foo except Baz?

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[gmhwxi]

How about:

#define Bar 1
#define Baz 30
#define Quz 16

abst@ype Foo(i:int) = int

macdef Bar = $extval (Foo(Bar), "1")

fun
foo{i:int | i != Bar} (x: Foo(i)): void = ...

[Shea Levy]

Ah, and how does the preprocessor know not to substitute in Bar in the LHS of the macdef?

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[gmhwxi]

Actually, I was not sure myself. I had to try it :)

The following style is probably better:

stadef Bar = 1 // Bar is static

abst@ype Foo(i:int) = int

macdef Bar = $extval (Foo(Bar), "1") // Bar is dynamic

fun
foo{i:int | i != Bar} (x: Foo(i)): void = ...

[Shea Levy]

Ah, I should probably read up on stadef :) Thank you!

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