Lisp to C conversion

[Charles Root]

I conjecture that you didn't hear much about Lisp to C conversion
because it isn't often done.  It is fairly common to do research using
a Lisp prototype and then build a second-generation system.  It would
be reasonable for this second-generation system to be in C.  However
the gains there are not due to conversion from Lisp to some other
language, but from using a more highly-tuned implementation.  There is
no reason to think that a simple translation from Lisp to C would gain
anything, if the original Lisp program was a sensible one.  Of course
if the original program was ill-suited to Lisp (e.g. floating point
array computations in a dialect of Lisp that doesn't do a good job
with this), then a translation might make sense.  The quality of
existing Lisp compilers seems about as good as existing C compilers.
Indeed the most widespread Lisp system that I know of (Utah's Portable
Standard Lisp) does more optimization than the most widespread C
system that I know of (various versions of PCC and Berkeley's
compilers).  The main limitation in the Lisp compilers I know about is
in dealing with heavy numerical computing.  This is not because the
compilers are stupid, but because of Lisp's nature as a typeless
language.  (Of course there are implementations that allow type
declarations.)