Numeric literals in other than base 10 - was Annoying octal notation

James Harris james.harris.1 at googlemail.com
Sat Aug 22 23:54:41 CEST 2009


On 22 Aug, 10:27, David <71da... at libero.it> wrote:

... (snipped a discussion on languages and other systems interpreting
numbers with a leading zero as octal)

> > Either hexadecimal should have been 0h or octal should
> > have been 0t :=)
>
>
> I have seen the use of Q/q instead in order to make it clearer. I still
> prefer Smalltalk's 16rFF and 8r377.
>
>
> Two interesting options. In a project I have on I have also considered
> using 0q as indicating octal. I maybe saw it used once somewhere else
> but I have no idea where. 0t was a second choice and 0c third choice
> (the other letters of oct). 0o should NOT be used for obvious reasons.
>
> So you are saying that Smalltalk has <base in decimal>r<number> where
> r is presumably for radix? That's maybe best of all. It preserves the
> syntactic requirement of starting a number with a digit and seems to
> have greatest flexibility. Not sure how good it looks but it's
> certainly not bad.
>
>
> >   0xff & 0x0e | 0b1101
> >   16rff & 16r0e | 2r1101
>
> > Hmm. Maybe a symbol would be better than a letter.

...

> >        Or Ada's        16#FF#, 8#377#...

> >        I forget if DEC/VMS FORTRAN or Xerox Sigma FORTRAN used x'FF' or
> >   'FF'x, and o'377' or '377'o

...

>
> What about 2_1011, 8_7621, 16_c26h or 2;1011, 8;7621, 16;c26h ?

They look good - which is important. The trouble (for me) is that I
want the notation for a new programming language and already use these
characters. I have underscore as an optional separator for groups of
digits - 123000 and 123_000 mean the same. The semicolon terminates a
statement. Based on your second idea, though, maybe a colon could be
used instead as in

  2:1011, 8:7621, 16:c26b

I don't (yet) use it as a range operator.

I could also use a hash sign as although I allow hash to begin
comments it cannot be preceded by anything other than whitespace so
these would be usable

  2#1011, 8#7621, 16#c26b

I have no idea why Ada which uses the # also apparently uses it to end
a number

  2#1011#, 8#7621#, 16#c26b#

Copying this post also to comp.lang.misc. Folks there may either be
interested in the discussion or have comments to add.

James



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