[mercury-users] Semantics of 'new'

[Douglas Auclair]

Hello, all,

In reviewing existential quantification, I can across the following code 
snippet:

:- type univ ---> some [T] mkuniv(T).

univ(X) = 'new mkuniv'(X).

I didn't see an explanation of 'new' in the neither the Language reference 
nor in the Library reference.  What are the semantics of 'new'?  For 
example, are the following two unifications the same?

:- type movie ---> dvd(string).

movies = List :-
  Animation = dvd("Emporer's New Groove"),  % not new
  Drama = 'new dvd'("Tadpole"),             % using new
  List = [Animation, Drama].

When does one use 'new' and when not?

Thanks.
Doug Auclair

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