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Help with Generic type constraints
f#compiler

Hello

I'm trying to add a IComparable constraint to keys in a map (following the example on page 212 of "Programming F#") like this..

type AVLmap<'key when 'key :> IComparable<'key>,'value> =
but the compiler rejects this (unexpected symbol ',' in type name). This works fine though..

type Foo<'key when 'key :> IComparable<'key>> =
as does this..

type AVLmap<'key,'value> =What am I missing here? Is this possible at all or am I doing something stupid?

Thanks

.

Constraints come at the end of the generic parameter list, so you want to do this:

1

type AVLmap<'key, 'value when 'key :> IComparable<'key>> = ...
By on 6/23/2010 6:18 AM ()

Constraints come at the end of the generic parameter list, so you want to do this:

1

type AVLmap<'key, 'value when 'key :> IComparable<'key>> = ...

Oh thanks. I should've thought to try that. I'm still a little confused about the syntax because AFAICS from the syntax for types on page 35 of the latest version of the language spec (2.0) my original is syntactically legal and the version you give is not (but works!). Is the spec correct re this I wonder?

type := long-ident<types> type when constraints(Though I guess that last one should in fact be..type when typar-constraints
)
types := type, ..., typeSo..types when (typar-)constraints.. is not legal syntax?

By on 6/23/2010 8:21 AM ()

The grammar definitions there are really confusing; what you actually want to look at is the typar-defns grammar element.

By on 6/23/2010 8:34 AM ()

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