[plt-scheme] (lib "foreign.ss") and vararg C functions

On Oct  7, Eli Barzilay wrote:
> On Oct  7, Matthias Felleisen wrote:
> > So one could create an "overloaded" printf library that picks up
> > from C?
> 
> Yes -- guessing the type according to the Scheme value.  The simple
> approach would be to look at the input types, construct a foreign
> interface and immediately apply it.  But it'll be better to cache
> the resulting interfaces.

Added to svn:
  http://svn.plt-scheme.org/plt/trunk/collects/ffi/c-printf.ss
with a usage example in
  http://svn.plt-scheme.org/plt/trunk/collects/ffi/examples/c-printf.ss

Also, C's printf is bad for your health, unless you parse the format
string and verify that it matches the types -- otherwise you can
always print a random number where a string is expected.  So this code
demonstrates how to provide `hidden' things, like foreign.ss's
bindings that are available only after `(unsafe!)'.

-- 
          ((lambda (x) (x x)) (lambda (x) (x x)))          Eli Barzilay:
                  http://www.barzilay.org/                 Maze is Life!