--- loncom/homework/caparesponse/caparesponse.pm	2012/03/05 11:50:39	1.252
+++ loncom/homework/caparesponse/caparesponse.pm	2012/12/14 11:17:09	1.253
@@ -446,6 +446,7 @@ sub check_submission {
     }
 
     my (@final_awards,@final_msgs,@names);
+    # $Apache::lonxml::debug = 1;	# DEBUG
     foreach my $name (keys(%answer)) {
 	&Apache::lonxml::debug(" doing $name with ".join(':',@{ $answer{$name}{'answers'} }));
 	
@@ -456,7 +457,6 @@ sub check_submission {
 	my ($result,@msgs) = 
 	    &Apache::run::run("&caparesponse_check_list()",$safeeval);
 	&Apache::lonxml::debug("checking $name $result with $response took ".&Time::HiRes::tv_interval($t0));
-        
 	&Apache::lonxml::debug('msgs are '.join(':',@msgs));
 	my ($awards)=split(/:/,$result);
 	my @awards= split(/,/,$awards);
@@ -465,6 +465,7 @@ sub check_submission {
 	push(@final_msgs,$msg);
 	push(@names,$name);
     }
+    # $Apache::lonxml::debug = 0;	# DEBUG
     my ($ad, $msg, $name) = &Apache::inputtags::finalizeawards(\@final_awards,
 							       \@final_msgs,
 							       \@names,1);
@@ -784,6 +785,19 @@ sub end_numericalresponse {
 		    $ans.=" $cleanunit";
 		}
 	    }
+	    #
+	    # The computer's response must be cast in a form that 
+	    # ensures it has sufficient significant figures.
+	    # the only way to do this is to sprintf it into scientific notation
+	    # due to the ambiguity of trailing zeros.
+	    # See Bug 6577
+	    #
+	    my ($sigMax, $sigmin) = &get_sigrange($Apache::inputtags::params{'sig'});
+	    my $sigfigs = $sigMax-1;
+
+	    for (my $i = 0; $i < scalar @$response; $i++) {
+		$response->[$i] = sprintf('%.' . $sigfigs . 'e', $response->[$i]);
+	    }
 	    my ($ad,$msg)=&check_submission($response,$partid,$id,$tag,
 					    $parstack,$safeeval);
 	    if ($ad ne 'EXACT_ANS' && $ad ne 'APPROX_ANS') {