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prove_rep_fn_onto                                              (Drule)
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prove_rep_fn_onto : thm -> thm

SYNOPSIS
Proves that a type representation function is onto (surjective).

DESCRIBE
If {th} is a theorem of the form returned by the function
{define_new_type_bijections}:

   |- (!a. abs(rep a) = a) /\ (!r. P r = (rep(abs r) = r))

then {prove_rep_fn_onto th} proves from this theorem that the
function {rep} is onto the set of values that satisfy {P}, returning the
theorem:

   |- !r. P r = (?a. r = rep a)




FAILURE
Fails if applied to a theorem not of the form shown above.

SEEALSO
Definition.new_type_definition, Drule.define_new_type_bijections,
Drule.prove_abs_fn_one_one, Drule.prove_abs_fn_onto,
Drule.prove_rep_fn_one_one.

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