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READ flushing atom delimiters


    Date: 30 May 1980 00:23-EDT
    From: David A. Moon <Moon at MIT-AI>
      .  .  .  I f the delimiter is a "useless" or "whitespace" character,
    it will be thrown away, rather than being UNTYI'ed back into the stream
    so that it can be TYI'ed later.  This will happen regardless of whether 
    the symbol or number is seen at top level or is inside of an expression,
      .  .  .
    Certain programs, such as reader macros, may be broken by this.  For them,
    a special variable which they may bind is provided.
    If READ-PRESERVE-DELIMITERS is bound non-NIL around a call to READ,
    all delimiters are preserved regardless of whether they are whitespace
    or meaningful characters.  .  .  .
    I would like to request a compatible change to Maclisp, to avoid 
    divergence and incompatibility on this point.
As it happens, GSB and I made this change to one version of a recent XLISP,
probably about version 1984 or so, but had to take it back when GSB
found he didn't have the time to accomodate his LMS and COBOL code.
What we were hoping to do was provide an additional function, say,
READ-AND-BREAK-CHAR, which would return both the item read and the
termination character.  For backwards compatibility, someone may raise
an objection to not haveing a "backwards-compatible-switch" (i.e.
READ-PRESERVE-DELIMITERS), but for future use, the explicit request
to return the termination character seems like a better approach for
those very few programs which want it.  Any comments?