Re: expr integer format always decimal?

[Bob Proulx]

Paul Eggert wrote:
> Bob Proulx writes:
> > However, I can't see anywhere that expr is defined to always read
> > integers as decimal values.
> 
> The current documentation says under "expr invocation"
> 
> Operands are either integers or strings.  Integers consist of one or
> more decimal digits, with an optional leading @samp{-}.
> 
> So yes, they're always decimal.  (POSIX requires this.)

I don't (yet) follow that reasoning.  Note that I don't want to change
the behavior of expr.  I am only pursuing the understanding of the
standard for expr.

The SUSv3 says the following:

  integer

  An argument consisting only of an (optional) unary minus followed by
  digits.

Neither that nor the info documentation says anything about a base for
the integer constants.  Since it is not specified why couldn't it use
the C rules the same as printf does?

  printf "%d\n" 010
  8

For printf that is the correct result because printf is defined to be
evaluated as a C constant as described by the ISO C standard.  Why
couldn't expr use the same interpretation of integer constants?

  expr 010
  8

Why wouldn't the this form above be conforming?  The integer consists
only of digits.  I can read nothing that says that is not an allowed
behavior.  Is there some catch-all in the SUS docs which say that
integers must be decimal?  Why can't integers be octal?

Bob