--- loncom/homework/default_homework.lcpm	2001/05/08 14:57:12	1.19
+++ loncom/homework/default_homework.lcpm	2001/05/31 20:47:50	1.24
@@ -3,8 +3,16 @@
 # 
 #
 #init some globals
+#
+# Guy Albertelli
+#
+# 05/25/2001 H. K. Ng
+# 05/31/2001 H. K. Ng
+#
 $RANDOMINIT=0;
 $pi=atan2(1,1)*4;
+$rad2deg=180.0/$pi;
+$deg2rad=$pi/180.0;
 
 sub caparesponse_check {
   my $answer='';  #done
@@ -116,6 +124,14 @@ sub tex {
   }
 }
 
+sub var_in_tex {
+  if ( $external::target eq "tex" ) {
+    return @_[0];
+  } else {
+    return "";
+  }
+}
+
 sub web {
   if ( $external::target eq "tex" ) {
     return @_[1];
@@ -128,6 +144,12 @@ sub web {
   }
 }
 
+sub html {
+  if ( $external::target eq "web" ) {
+    return @_[0];
+  }
+}
+
 sub problem {
   return '1';
 }
@@ -144,18 +166,63 @@ sub random {
   return $result;
 }
 
+sub abs { abs(shift) }
+sub sin { sin(shift) }
+sub cos { cos(shift) }
+sub exp { exp(shift) }
+sub int { int(shift) }
+sub log { log(shift) }
+sub atan2 { atan2($_[0],$_[1]) }
+sub sqrt { sqrt(shift) }
+
 sub tan  { sin($_[0]) / cos($_[0]) }
-sub atan { atan2($_[0], 1); }
-sub acos { atan2(sqrt(1 - $_[0] * $_[0]), $_[0] ); }
-sub asin { atan2($_[0], sqrt(1- $_[0] * $_[0]) );  }
+#sub atan { atan2($_[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 html {
-  if ( $external::target eq "web" ) {
-    return @_[0];
-  }
+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 $b } @_;
+    return pop @sorted;
+}
+
+sub roundto {
+    my ($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); }
@@ -184,13 +251,120 @@ sub map {
   }
 }
 
+sub capa_id { return }
+
+sub problem { return }
+
+sub name{
+  my $fullname = &EXT('environment.lastname').', '.&EXT('environment.firstname').' '.&EXT('environment.middlename');
+  $fullname = "" if $fullname eq ",  ";
+  $fullname =~ s/\%2d/-/;
+  return $fullname;
+}
+
+sub student_number { 
+  my $id = &EXT('environment.id');
+  $id = '' if $id eq "";
+  return $id;
+}
+
+sub class {
+  my $course = &EXT('course.description');
+  $course = '' if $course eq "";
+  return $course;
+}
+
+sub sec { 
+  my $sec = &EXT('request.course.sec');
+  $sec = '' if $sec eq "";
+  return $sec;
+}
+
+sub open_date { 
+  my @dc = split(/\s+/,localtime(&EXT('resource.0.opendate')));
+  return '' if ($dc[0] eq "Wed" and $dc[2] == 31 and $dc[4] == 1969);
+  my @hm = split(/:/,$dc[3]);
+  my $ampm = " am";
+  if ($hm[0] > 12) {
+    $hm[0]-=12;
+    $ampm = " pm";
+  }
+  return $dc[0].', '.$dc[1].' '.$dc[2].', '.$dc[4].' at '.$hm[0].':'.$hm[1].$ampm;
+}
+
+sub due_date { 
+  my @dc = split(/\s+/,localtime(&EXT('resource.0.duedate')));
+  return '' if ($dc[0] eq "Wed" and $dc[2] == 31 and $dc[4] == 1969);
+  my @hm = split(/:/,$dc[3]);
+  my $ampm = " am";
+  if ($hm[0] > 12) {
+    $hm[0]-=12;
+    $ampm = " pm";
+  }
+  return $dc[0].', '.$dc[1].' '.$dc[2].', '.$dc[4].' at '.$hm[0].':'.$hm[1].$ampm;
+#  return $dc[0].', '.$dc[1].' '.$dc[2].', '.$dc[4].' at '.$dc[3];
+}
+
+sub answer_date { 
+  my @dc = split(/\s+/,localtime(&EXT('resource.0.answerdate')));
+  return '' if ($dc[0] eq "Wed" and $dc[2] == 31 and $dc[4] == 1969);
+  my @hm = split(/:/,$dc[3]);
+  my $ampm = " am";
+  if ($hm[0] > 12) {
+    $hm[0]-=12;
+    $ampm = " pm";
+  }
+  return $dc[0].', '.$dc[1].' '.$dc[2].', '.$dc[4].' at '.$hm[0].':'.$hm[1].$ampm;
+#  return $dc[0].', '.$dc[1].' '.$dc[2].', '.$dc[4].' at '.$dc[3];
+}
+
+sub array_moments {
+  my @input=@_;
+  my (@output,$N);
+  $N=scalar (@input);
+  $output[0]=$N;
+  if ($N <= 1) {
+    $output[1]=$input[0];
+    $output[1] = "Input array not defined" if ($N == 0);
+    $output[2]="variance undefined for N<=1";
+    $output[3]="skewness undefined for N<=1";
+    $output[4]="kurtosis undefined for N<=1";
+    return @output;
+  }
+  my $sum=0;
+  foreach my $line (@input) {
+    $sum+=$line;
+  }
+  $output[1] = $sum/$N;
+  my ($x,$sdev,$var,$skew,$kurt) = 0;
+  foreach my $line (@input) {
+    $x=$line-$output[1];
+    $var+=$x**2;
+    $skew+=$x**3;
+    $kurt+=$x**4;
+  }
+  $output[2]=$var/($N-1);
+  $sdev=sqrt($output[2]);
+  if ($sdev == 0) {
+     $output[3]="inf-variance=0";
+     $output[4]="inf-variance=0";
+     return @output;
+  }
+  $output[3]=$skew/($sdev**3*$N);
+  $output[4]=$kurt/($sdev**4*$N)-3;
+  return @output;
+}
+
 sub choose {
   my $num = $_[0];
   return $_[$num];
 }
+
 #$external::randomseed=time;
 #$a=2;
 #$b=2;
 #$c=2;
 #&map(1,\$a,\$b,\$c,3,4,5);
 #print $a."\n".$b."\n";
+
+