Opening files with Cscheme

[Les Milash <unicads!les@boulder.colorado.edu>]

i have a thing called CScheme, which i love.  i have a manual called
RRRS.  i have a problem.

i'm trying to write a program that's c-preprocessor compatable, in that
it takes a -I/parameter -I/that/lists/a/bunch -I/of/directories/that
include files might be in.  so when the code includes foo.h i have to
find the first one of
	/parameter/foo.h
	/that/lists/a/bunch/foo.h
	/of/directories/that/foo.h
that exists.

RRRS talks about (open-input-file "filename") but if the file doesn't exist
i get an "out of range with "filename"" error and the program stops.

is there a way to figure out if some file exists without crashing?  or
some way to substitute some better error behaviour (i'd just as soon
have it return '() or #!the-you-screwed-up-object or something).
i have the CScheme source and am not adverse to making myself un-scheme-
compatable (but i imagine that scheme can do what i want somehow (else
what good is it?))

thanks in advance for the assistance!

Les Milash

wow! with a language like this, i might even be able to handle 
a shared-memory multiprocessor!