X_SKOLEM_CONV
Conv.X_SKOLEM_CONV : (term -> conv)
Introduces a user-supplied Skolem function.
X_SKOLEM_CONV takes two arguments. The first is a variable f, which
must range over functions of the appropriate type, and the second is a
term of the form !x1...xn. ?y. P. Given these arguments,
X_SKOLEM_CONV returns the theorem:
|- (!x1...xn. ?y. P) = (?f. !x1...xn. tm[f x1 ... xn/y])
which expresses the fact that a skolem function f of the universally
quantified variables x1...xn may be introduced in place of the the
existentially quantified value y.
Failure
X_SKOLEM_CONV f tm fails if f is not a variable, or if the input
term tm is not a term of the form !x1...xn. ?y. P, or if the
variable f is free in tm, or if the type of f does not match its
intended use as an n-place curried function from the variables
x1...xn to a value having the same type as y.