Re: Why would anyone want opacity?

[Guillermo J. Rozas <gjr@martigny.ai.mit.edu>]

|   Cc: blume@cs.Princeton.EDU, rrrs-authors@martigny.ai.mit.edu
|   Date: Thu, 09 May 96 17:21:45 -0400
|   From: "ozan s. yigit" <oz@nexus.yorku.ca>
|
|   type checking /is/ a property of tools, but type information is a component
|   of languages. in some natural languages, type information (say, gender) is
|   inferred and in some, it is explicitly stated. so why should artifical
|   natural languages be any different?

Sure enough.  You can't use + on strings in standard Scheme.
The type information is there.  The restrictions are not.