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implementation module dnc
// $Id$
import graph
import StdEnv
// dnc is like varcontents, but can give a more reasonable error message
// when the contents is used when undefined.
dnc :: (var->.String) !.(Graph sym var) var -> (.Bool,Node sym var) | == var
dnc makemessage graph var
| fst vc = vc
= (False,(wrong "symbol",wrong "arguments"))
where vc = varcontents graph var
wrong element = abort ("getting "+++element+++" of free variable: "+++makemessage var)
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