Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!cs.utexas.edu!uunet!yale!haveraaen-magne
From: haveraaen-magne@CS.YALE.EDU (Magne Haveraaen)
Newsgroups: comp.lang.pascal
Subject: Re: I/O (was Re: Standard Pascal)
Message-ID: <66532@yale-celray.yale.UUCP>
Date: 15 Jul 89 15:50:03 GMT
Sender: root@yale.UUCP
Reply-To: haveraaen-magne@CS.YALE.EDU (Magne Haveraaen)
Organization: Yale University Computer Science Dept, New Haven CT  06520-2158
Lines: 36

There are more ways to implement interactive I/O in Pascal than hitherto
discussed on the net.  A very simple and powerful scheme is as follows
(and it was implemented in ND-Pascal from Norsk Data):

Assume the input file of every program is initialized with the rest of the
program call line. If there are no parameters, the input buffer will be
initialized with an eoln (the return character you entered after the
program name to start program execution). If some program parameters where
given, these would comprise the first line, and would be readable with
Pascal's read procedures. The scheme for writing a interactive dialogue
would be (as already suggested on the net):

	:
	writeln('question 1');
	readln; (*synchronize on first line*)
	read(answer);
	process(answer);
	writeln('question 2');
        readln; (*synchronize on next line*)
        read(answer);
        process(answer);
	:

In Sun Pascal (and other unix Pascals) one must omit the first "readln" in
a dialogue, creating an unnecessary special case. This is aggravating if
you e.g.  want to have a general read-procedure that checks input and
repeats the question if errors are made.

Another advantage of this approach is that program parameters may now be
read by Pascal's standard read procedures. This makes it very simple to
read an integer parameter. And if you are so unixified that you have to
look in an array for the program's parameters - well it is fairly easy
creating a procedure that will initialize the global array by reading the
initial line.

Magne		<haveraaen@cs.yale.edu>