Pattern matching, implict par. question

[Jorge Adriano]

Hello, When trying 

type CTPar = ([Double],Int,Int)
ctPar          ::(?ctPar::CTPar)=>CTPar 
ctPar@(us,n,j) = ?ctPar

I got this error message in ghci is:
"    Illegal overloaded type signature(s)
        in a binding group for ctPar, us, n, j
        that falls under the monomorphism restriction
    When generalising the type(s) for ctPar, us, n, j
Failed, modules loaded: CrossTypeOps."

Should the monomorphis restriction really apply here?
The values of us,j,n do depend on the context, but not their types (right?).

J.A.