Subject: Re: siod, adding scheme standard procedures?
From: (Rob Warnock)
Date: 1999/02/21
Newsgroups: comp.lang.scheme
Message-ID: <7aove9$>
Bengt Kleberg <> wrote:
| Is there a procedure library available for siod, that 'emulates' R4RS
| procedures? Like (list-ref ...), (open-input-file ...)?

No, and there really can't be -- at least, not without a *lot* of hacking
on the internals of SIOD. Oh, sure, you can wrap some syntactic sugar
around some of the differences with procedure & macro definitions, but
there are some really fundamental things -- whether you call them bugs,
features, or simplifications depends on what you're trying to do that
day -- that just don't map to R4RS well enough that you could ever hope
to pass, say, Jaffer's "r4rstest.scm". Here are a few:

- Symbols are case-sensitive; there's no provision (that I could find)
  for turning that off.

- Numbers are C doubles. Only. No bignums. No "exacts". Where an exact
  integer is needed (e.g., as a list or array index), the C double is
  silently coerced to a C long [truncated]. Where the functionality of
  R4RS "exact?" is needed (internally, since it's not exposed to the user),
  say, for deciding whether to print a decimal point or not, it's defined
  as being able to coerce the number to a C long and back to a float and
  get the identical original float back.

- There is no separate character type; numbers are used (as in C),
  silently coerced to int. E.g., (putc 65.43) prints an "A".

- There is no separate boolean type. #t == 1.0 and #f == nil == ().
  The symbol 't is bound to itself, so it also is true when used in
  a boolean context, but it's not literally "1.0" the way "#t" is.
  And while "nil" isn't a number per se, due to the way the subroutine
  calls are done it's treated as "zero". So (+ 4 3 #f 2 #t 1) ==> 11
  (with no error reported).

That is *NOT* to say that SIOD is not a useful, small, fast-startup
[though slower-running] dialect of Scheme that's easy to glue to C code,
and that comes with some nice extensions for networking & web hacking &
database interfacing. It is!  None of the above "features" get in the
way of using it as a small scripting language. But it's really not very
close to R4RS...


Rob Warnock, 8L-855
Applied Networking
Silicon Graphics, Inc.		Phone: 650-933-1673
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