#!/usr/bin/env perl

# This script shows a problem with Maple and pty's. Usually the input is
# echoed twice, hence the regexp /.*?EndOfInput:.*?EndOfInput:/ below.
# But the input is sometimes echoed only once (at a random iteration),
# with the consequence that this script freezes.

use strict;
use IPC::Run;

my ($pty, $ptyin, $ptyout);
my @maple = ($ENV{'MAPLE'} || 'maple', '-q', '-s');
$pty = IPC::Run::start(\@maple, '<pty<', \$ptyin, '1>pty>', \$ptyout);

sub maple_wr
  {
    warn "--> maple_wr(@_)\n";
    my $in = "@_ EndOfInput:\n";
    $ptyin = $in;
    pump $pty while length $ptyin ||
      ($ptyout =~ tr/\r//d,
       warn("--> [$ptyout]\n"),
       $ptyout !~ s/.*?EndOfInput:.*?EndOfInput://s);
    warn "--> maple_wr OK\n";
  }

sub maple_rd
  {
    @_ and &maple_wr(@_);
    pump $pty while $ptyout !~ s/^\s*(\S.*?)\s*$//;
    warn "--> maple_rd [$1]\n";
    return $1;
  }

&maple_rd("interface(prettyprint=0,screenwidth=9999): Digits := 60: 1;") == 1
  or die;

my $e = "1.0";
foreach (1..300)
  {
    warn "--> Iteration $_\n";
    $e = "cos($e)";
    &maple_rd("$e;") or die;
  }

# $Id: pty-bug 11877 2006-04-14 19:52:38Z lefevre $