[WIP] AnyOf Operator

[AdamSpeight2008]

AnyOf Operator

This is a generalisation of Proposal #23 to allow other usage cases.

The AnyOf operator as two modes of usage, as a :=

• Binary Operator left AnyOf right
• Unary Prefix Operator AnyOf right

---

Binary Operator

This is provides the equivalent of an = against a single instance and collection of instance, of some type.

Example Usage
Consider the following code., where we are checking the part.Kind is one of a set of values.
Exisiting

previousWasClass = ( part.Kind = SymbolDisplayPartKind.ClassName )     OrElse
                   ( part.Kind = SymbolDisplayPartKind.InterfaceName ) OrElse
                   ( part.Kind = SymbolDisplayPartKind.StructName )

What if we express that in a more operator like form.
Proposed

previousWasClass = part.Kind AnyOf {SymbolDisplayPartKind.ClassName,
                                    SymbolDisplayPartKind.InterfaceName,
                                    SymbolDisplay}

The code produced by both are functionally equivalent

---

Today this functionality (not syntax) via extension method

<Extension()>
Function AnyOf( p As SymbolDisplayPartKind, paramarray these() as SymbolDisplayPartKind) As Boolean
  For i = 0 To these.length - 1
    If p = these(i) Then Return True
  Next
End Function

---

Unary Operator

The primary usage target of this prefix is in TypeOf obj Is ... expressions.
Existing

(TypeOf obj Is T0) OrElse (TypeOf obj Is T1) OrElse (TypeOf obj Is T2) ...
(TypeOf obj IsNot T0) AndAlso (TypeOf obj IsNot T1) AndAlso (TypeOf obj IsNot T2) ...

Proposed

 TypeOf obj Is AnyOf { T0, T1, T2 ... }
 TypeOf obj IsNot AnyOf { T0, T1, T2 ... }

---

Implementation

The compiler treats them as syntactic sugar for the exist code. Just that we let the compiler build the underlying expression itself. It then could choose to implement the expression using the operators = and <> or if the object is IComparable/IComparable(Of T) via o.ComparedTo( x ) = 0 or EqualTo( ).

[Echo-8-ERA]

Isn't your binary operator basically the IN operator from SQL? obj In collection is more intuitive than obj AnyOf collection while reusing an existing keyword.
Your unary operator could also reuse the In keyword and from what I can tell, keeps the spirit of your proposal intact.

[AdamSpeight2008]

@Echo-8-ERA It is just like the In operator from SQL.

[zspitz]

@AdamSpeight2008

I think the usage your AnyOf operator is unclear, in that there are multiple possibilities for what goes on the right side -- the right hand side can be an array of values, or a curly-brace-wrapped set of type names (which is definitely not an array).

---

This could be resolved by leaving AnyOf exclusively for type-checking, and reusing the In keyword for the value-comparison usage, like @Echo-8-ERA suggests:

If part.Kind In {SymbolDisplayPartKind.ClassName,
                                    SymbolDisplayPartKind.InterfaceName,
                                    SymbolDisplay} Then
End If

and extended to any IEnumerable(Of T):

Dim i=5
Dim range = Enumerable.Range(1,5)
If i In range Then
End If

See my comment here.

[AdamSpeight2008]

Using .Range(1,5) then .Contains(..) over a contiguous set of values, seems to (me) inefficient
When it could be simpler to express as a Bounds of Limits. eg 1 <= x <= 5

[zspitz]

@AdamSpeight2008 Of course, but the idea is that the pattern can be extended very simply:

Dim i=5
Dim squares = Enumerable.Range(1,5).Select(Function(x) x*x)
If i in squares Then
End If

[AdamSpeight2008]

@zspitz I was thinking of an type the did represent Bounds / Limits. It could implement IEnumerable so it as access to the LINQ to Objects extension methods.

[ghost]

@AdamSpeight2008

TypeOf obj Is AnyOf { T0, T1, T2 ... }
TypeOf obj IsNot AnyOf { T0, T1, T2 ... }

This is already possible:

{T0.GetType, T1.GetType, T2.Gettype, ...}.contains(obj.GetType)
Not {T0.GetType, T1.GetType, T2.Gettype, ...}.contains(obj.GetType)

Same for:

previousWasClass = ( part.Kind = SymbolDisplayPartKind.ClassName ) OrElse
( part.Kind = SymbolDisplayPartKind.InterfaceName ) OrElse
( part.Kind = SymbolDisplayPartKind.StructName )

{SymbolDisplayPartKind.ClassName, 
 SymbolDisplayPartKind.InterfaceName, 
 SymbolDisplayPartKind.StructName}.contains(part.Kind)

[zspitz]

@tverweij Presumably you mean: {GetType(T0), GetType(T1), GetType(T2)}.Contains(obj.GetType) But this is not quite the same. If `obj.GetType` represents a type which inherits or implements `T0`, then `TypeOf obj Is T0` would evaluate to `True`, even though `obj.GetType = GetType(T0)` would evaluate to `False`. Similarly, `TypeOf obj Is AnyOf {T0, T1, T2}` would also evaluate to `True` if `obj.GetType` would inherit/implement any of `T0`, `T1`, or `T2`.

…

________________________________ From: Theo Verweij <notifications@github.com> Sent: Thursday, November 30, 2017 2:05 PM To: dotnet/vblang Cc: Zev Spitz; Mention Subject: Re: [dotnet/vblang] [WIP] `AnyOf` Operator (#75) @AdamSpeight2008<https://github.com/adamspeight2008> TypeOf obj Is AnyOf { T0, T1, T2 ... } TypeOf obj IsNot AnyOf { T0, T1, T2 ... } This is already possible: {T0.GetType, T1.GetType, T2.Gettype, ...}.contains(obj.GetType) Not {T0.GetType, T1.GetType, T2.Gettype, ...}.contains(obj.GetType) Same for: previousWasClass = ( part.Kind = SymbolDisplayPartKind.ClassName ) OrElse ( part.Kind = SymbolDisplayPartKind.InterfaceName ) OrElse ( part.Kind = SymbolDisplayPartKind.StructName ) {SymbolDisplayPartKind.ClassName, SymbolDisplayPartKind.InterfaceName, SymbolDisplayPartKind.StructName}.contains(part.Kind) — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub<#75 (comment)>, or mute the thread<https://github.com/notifications/unsubscribe-auth/AATDZln8azaY1DK40jU6nByWnT-thgM0ks5s7rY6gaJpZM4Nd-oI>.