CODEWITHSUNDEEP
genericsf#operatorsexplicittype-parameter
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controlflow

Reputation: 6737

F#: explicit type parameters in operator binding

I'm trying to define operator with the explicit type parameters and constraints:

let inline (===)<'a, 'b
    when 'a : not struct
     and 'b : not struct> a b = obj.ReferenceEquals (a,b)

It works well in F# 2.0, but produces the:

warning FS1189:
 Type parameters must be placed directly adjacent to the type name, e.g. "type C<'T>", not type "C <'T>"

So what is the right way to do explicit type arguments specification for operator definition?

p.s. Please don't tell me about implicit type parameters and some other workarounds, I want to solve concretely this issue.

Upvotes: 12

Views: 399

Answers (2)

Brian
Brian

Reputation: 118865

A bug in the compiler means that symbolic operators are never considered directly adjacent to type parameters. You can workaround via e.g.

let inline myeq<'a, 'b 
    when 'a : not struct 
    and 'b : not struct> a b = obj.ReferenceEquals (a,b) 

let inline (===) a b = myeq a b

Upvotes: 13

Mark H
Mark H

Reputation: 13897

let inline (===) (a : 'TA when 'TA : not struct) (b : 'TB when 'TB : not struct) = 
    obj.ReferenceEquals (a,b)

Upvotes: 4

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