(set-macro-char #\, (get-macro-char #\,) t)

  This meant 123,456,789 read back as the symbol named "123,456,789"
  which is almost exactly half as useful as what I had in mind.  So I
  hacked the function that I thought made the wrong decision about
  numberhood of this string.  The rest of the system was not amused,
  so I had to delete the commas from the input at a fairly low level,
  but that's not too satisfactory, as it's common in some cultures to
  use dot or space, not comma, for grouping (silly Europeans!), and
  parse-integer could really use some more options.  Like a cancer my
  wish list item grew, so here's the condensed and sanitized version
  of with wish list item:

  I'd like integers printed with internal commas for grouping to be
  readable as if the commas were absent.  This requires the comma to
  be a non-terminating macro character, which _could_ cause problems
  with space-deficient legacy code.  It would be nice if more of the
  system would grok human-readable numbers, and I would be positively
  thrilled if write and friends would do grouping, not just format.

  Unfortunately, this requires rather low-level changes to most Common
  Lisp implementations, so I'm asking for reactions and suggestions.

        100,000.00

(of course that should probably really be a scaled integer or
something if it's a financial calculation, but...)

HP calculators offer the two options of comma for separator and point
for point and the other way around, are there other common choices in
use?

I was going to say that it doesn't really affect whether the char is a
readmacro because it only matters in number parsing and that's kind of
magic anyway, but apart from this being obviously wrong, it's also bad
if something like comma could be used for decimal point then there's a
whole nightmare there with anything like `(,1), which seems to me to
be genuinely ambiguous (in the sense that, if comma was decimal point,
I would not know what it should mean) so I don't know how to deal with
that...

(I don't think that Erik was asking for the  additional hairiness of
being able to choose the point & grouping chars, probably because he
thought about this harder than me!)

Use the FFI to call a Java program that uses that language's library for
reading the numbers?  Then modify the readtable for 0-9, + and - to read
something and then call that parser.

  I'm sorry to say this, but you need to understand how the reader
  works before you can make useful suggestions.

Erik,

I confirm the need (you and others provided me with FORMAT examples for
currency amount printing) and agree with the need for configurability.
An OT question:

* Example: 4,288
  Non-example: "The state deficit of Andorra was EUR 423.234.544,95 in
1999"

So many rants just ramble along, switching from topic to topic,
spewing bad grammar and worse spelling, and generally making no
sense whatever.  This one was focused, well-written, and included
wonderfully biting sarcasm!

Of course, the fact that I too disdain linguistic inanity had
nothing to do with my enjoyment of your rant...  :)

J.B.

--
John Watton
Alcoa Inc.

The problem with comma is that 1,000 is a meaningful number to people in
some locales and means what 1.000 means to us.  A sufficient case could be
made that comma in numbers be allowed as a synonym for "." that I'd rather
just not allow it in numbers at all.  It just invites people to think in
a non-computery way about numbers, but there are multiple non-computery
ways to think, and so it invites people to quarrel over whose non-computery
way should dominate.

Not to mention the incompatibility of things like `(100,200).  Though I
doubt many exploit that.