Hi,

Given two record types that are identical but in name, is it safe (if perhaps a poor idea) to cast between functions that are parametric in these record types:

e.g. Given, 

module A = 

struct

  type t = {a:int}

end

module B = 

struct

  type t = {a:int}

end

Is this safe ? 

module F(Ty: sig type t = {a:int} end) =

struct

  let extract {Ty.a=x} = x

end

module F_A = F(A)

let y = {B.a=3}

(Obj.magic F_A.extract) y

Put another way:  is the implementation of two records w/ identical labels the same, or is there a runtime significance to their static difference?

Thanks,

Yitzhak

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Yitzhak Mandelbaum

AT&T Labs - Research

http://www.research.att.com/~yitzhak