--- loncom/homework/default_homework.lcpm	2001/05/08 14:57:12	1.19
+++ loncom/homework/default_homework.lcpm	2001/05/25 21:20:19	1.20
@@ -3,6 +3,12 @@
 # 
 #
 #init some globals
+#use Math::Trig;
+#
+# Guy Albertelli
+#
+# 05/25/2001 H. K. Ng
+#
 $RANDOMINIT=0;
 $pi=atan2(1,1)*4;
 
@@ -149,6 +155,31 @@ sub atan { atan2($_[0], 1); }
 sub acos { atan2(sqrt(1 - $_[0] * $_[0]), $_[0] ); }
 sub asin { atan2($_[0], sqrt(1- $_[0] * $_[0]) );  }
 sub log10 { log($_[0])/log(10); }
+sub factorial {
+    my $input = int(shift);
+    return "Error - unable to take factorial of an negative number ($input)" if $input < 0;
+    return "Error - factorial result is greater than system limit ($input)" if $input > 170;
+    return 1 if $input == 0;
+    my $result = 1; 
+    for (my $i=2; $i<=$input; $i++) { $result *= $i }
+    return $result;
+}
+
+sub sgn {
+    return -1 if $_[0] < 0;
+    return 0 if $_[0] == 0;
+    return 1 if $_[0] > 0;
+}
+
+sub min {
+    my @sorted = sort { $a <=> $b || $a cmp $b } @_;
+    return shift @sorted;
+}
+
+sub max {
+    my @sorted = sort { $a <=> $b || $a cmp $b } @_;
+    return pop @sorted;
+}
 
 sub html {
   if ( $external::target eq "web" ) {
@@ -156,6 +187,21 @@ sub html {
   }
 }
 
+sub roundto {
+    my ($input,$n) = @_;
+    return sprintf('%.'.$n.'f',$input);
+}
+
+sub to_string {
+    my ($input,$n) = @_;
+    return sprintf('%'.$n,$input) if $n ne "";
+    return sprintf($input) if $n eq "";
+}
+
+sub sub_string {
+    my ($str,$start,$len) = @_;
+    return substr($str,$start-1,$len);
+}
 
 sub pow   {return $_[0] ** $_[1]; }
 sub ceil  {return (($_[0]-int($_[0]))== 0.0) ? $_[0] : (int($_[0])+ 1); }