[cvs-nhc98] patch applied (hat): Make hat-detect work again, using the new file format for hat versions > = 2.00.

[Malcolm Wallace]

Sun May  4 07:55:43 PDT 2003  malcolm
  * Make hat-detect work again, using the new file format for hat versions >= 2.00.
  
  This preliminary re-implementation of hat-detect is not yet fully
  featured.  It allows answering questions yes or no, but does not yet
  support "maybe".  Nor does it support memoisation of previously-seen
  answers.
  
  However, it does deal (nearly) correctly with asking about the
  application of trusted functions.  A trusted application should not be
  asked as a question unless it has suspect children - the vast majority
  of trusted applications do not, but it is expensive to determine
  accurately.  In fact, we use an approximation to determine whether
  the trusted application has untrusted children.  Rather than searching
  the whole file looking for such children, we reason that the only way
  for such children to arise is in a higher-order application where the
  untrusted function is passed as an argument.  Thus, when determining
  the trustedness of the function symbol, we simply extend the check a
  little to determine the trustedness of all function symbols within the
  (most evaluated form of the) arguments as well.

    A ./src/hattools/Detect.hs
    M ./src/hattools/HatDetect.hs -327 +322
    M ./src/hattools/Makefile -35 +33
    A ./src/hattools/detectutils.c
    A ./src/hattools/parentset.c
    A ./src/hattools/parentset.h