Re: fork in Lisp? was: Maxima servermode: stability of commands....

Hi Robert,

On May 10, 2006, at 5:52 PM, Robert Dodier wrote:
>
>> The server mode should also provide a more predictable command/answer
>> sequence and leave out the line counters (%oN) and prompts ($iN), as
>> well as all the whitespace.
>
> Not sure what you mean here. Maybe you can post a more detailed
> message about this.

As an example:

[www at phy1 www]$ maxima
Maxima 5.9.2.99rc1 http://maxima.sourceforge.net
Using Lisp SBCL 0.9.10
Distributed under the GNU Public License. See the file COPYING.
Dedicated to the memory of William Schelter.
This is a development version of Maxima. The function bug_report()
provides bug reporting information.
(%i1) 42;
(%o1)                                 42
(%i2) x^2+2x^2;
Incorrect syntax: x is not an infix operator
(%i2) (%o2)                                    2
(%i3) 17;
(%o3)                                 17
(%i4) x^2+2*x^2;
                                         2
(%o4)                                3 x
(%i5) quit();
[www at phy1 www]$

On the screen in an interactive session, this is all just fine and  
looks nice. But in server mode:

* we don't need a welcome message
* the (%i1) etc should not be produced
* the (%o1) etc should not be produced
* the syntax error should not mess up the sequence, i.e., the line  
starting with (%i2) (%o2) should not be produced
* the pretty print should be disabled
* Errors should start with something that clients can easily  
identify, e.g., "ERROR:"

So in server mode, the same sequence would look like this (without  
the "Input:", "Output:" and quotation marks):

Input: "42;"
Output: "42"
Input: "x^2+2x^2;"
Output: "ERROR: Incorrect syntax: x is not an infix operator"
Input: "17;"
Output: "17"
Input: "x^2+2*x^2;"
Output: "3*x^2"

I guess what I am trying to say is that since it's not a human at the  
other end, the communication needs to be terse and very predictable:  
one input command produces one line of output.

- Gerd.