[Aldor-l] Reading from stdin

[Christian Aistleitner]

Hello,

in a private Email I have been asked, about reading from stdin. As it  
probably applies to other people as well, I decided to answer to the list.

The naive approach via

#include "aldor"

import from TextReader;
import from TextWriter;
import from String;
import from Character;

local str: String := << stdin;

stdout << "Received: " << str << newline;

Gives problems, as it does not necessarily give the whole line:

____________________________________________
tmgisi at spencer
cwd: ~
$ LC_ALL=C /opt/aldor/bin/aldor -M no-abbrev -C args=-Wopts=-m32 -Ffm \
-Fx -lalgebra -laldor test2.as && ( echo 3/4 | ./test2 )
cc1: note: -fwritable-strings is deprecated; see documentation for details
cc1: note: -fwritable-strings is deprecated; see documentation for details
Received: 3


You'll have to use quotes to achive this:

____________________________________________
tmgisi at spencer
cwd: ~
$ LC_ALL=C /opt/aldor/bin/aldor -M no-abbrev -C args=-Wopts=-m32 -Ffm \
-Fx -lalgebra -laldor test2.as && ( echo \"3/4\" | ./test2 )
cc1: note: -fwritable-strings is deprecated; see documentation for details
cc1: note: -fwritable-strings is deprecated; see documentation for details
Received: 3/4

Forcing users to quote things is nasty. For the CharSet library I used the  
following function:

readString():String == {
	import from Character;
	import from MachineInteger;

	local ret : String := empty;
	local ch : Character;
	
	ch := <<$Character stdin;
	while ch ~= newline repeat
	{
		ret := ret + ch::String;
		ch := <<$Character stdin;
	}
	ret;
}

It reads _every_ character until a newline occurs. The returned string  
does not contain a trailing newline:

____________________________________________
tmgisi at spencer
cwd: ~
$ LC_ALL=C /opt/aldor/bin/aldor -M no-abbrev -C args=-Wopts=-m32 -Ffm -Fx  
-lalgebra -laldor test3.as && ( echo 3/4 | ./test3 )
cc1: note: -fwritable-strings is deprecated; see documentation for details
cc1: note: -fwritable-strings is deprecated; see documentation for details
Received: 3/4

On systems with suitable readline support (Every 32-bit GNU/Linux system  
should do), you can use something like:

#include "aldor"

import from TextReader;
import from TextWriter;
import from String;
import from Character;

Readline: with {
     (<<): ( prompt: String == "" ) -> String;
} == add {

     import {
	readline: String -> String;
     } from Foreign C;

     (<<)( prompt ): String == {
	readline( prompt );
     }
}

import from Readline;

local str: String := <<();

stdout << "Received: " << str << newline;


to take advantage readline. I could not test the readline snippet, as I do  
not have 32-bit version of readline -- still waiting for 64-bit Aldor.

--
Kind regards,
Christian