Re: The GP command “?”

[Ilya Zakharevich <nospam-abuse@ilyaz.org>]

On Sat, Dec 09, 2023 at 07:49:50PM -0800, Ilya Zakharevich wrote:
>   The GP calculator accepts input in the PARI language, as well as
>   special commands starting with \ or with ? or with #.  The PARI
>   language has unary and binary operators (among them + - * / % << >>
>   && || < > == <= >=) “with the usual meaning” (and the assignment
>   flavors such as +=) and other operators (inspect the output of ?19
>   or ?_\_ or ?_! or ?_===_  etc. for details).  The command separator
>   is “;”.
> 
>   Thousands of available functions are split into “topics” (inspect
>   them via the list emitted by the command ?sections).  User-defined
>   functions (listed by ?0) are stored in variables (like f below) and
>   are defined as:
>     f(mandatory_arg, optional_arg=default) = N++; mandatory_arg+optional_arg
>   or equivalently (omit parentheses if this terminates a command):
>     (f = (mandatory_arg, optional_arg=default) -> N++; mandatory_arg+optional_arg)
>   Flow control is via functions if(), while() etc. (inspect ?if
>   etc. — and output of ?1).

Another important thing which should better be mentioned is variables
vs. “ring generators” (is there a proper PARI's nomenclature?).  Like

  “Free variables” for polynomials/series/rational functions etc. are
  denoted as 'z etc.  As a shortcut, this is the default value of the
  corresponding unassigned global variables (so they behave as if
  after z='z).

Should not there be a warning about variables?

  Warning: polynomials in several variables are treacherous (see
  ????polynomials).

"????" since I do not know where to refer the reader to…

Yours,
Ilya