loncom/homework/functionplotresponse.pm - diff

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-version 1.14, 2010/10/17 22:32:19
+version 1.15, 2010/10/19 02:04:27
  Line 453  sub get_answer_from_form_fields {
     return ($answer,%coords);
  }
+ #
+ # The following functions calculate the cubic-hermite splines server-side
+ #
+ sub cubic_hermite {
+    my ($t,$p1,$s1,$p2,$s2)=@_;
+    return (2.*$t*$t*$t-3.*$t*$t+1.)*$p1 + 5.*($t*$t*$t-2.*$t*$t+$t)*($s1-$p1)+
+           (-2.*$t*$t*$t+3.*$t*$t)  *$p2 + 5.*($t*$t*$t-$t*$t)      *($s2-$p2);
+ }
+ #
+ # d/dt(...)
+ #
+ sub ddt_cubic_hermite {
+    my ($t,$p1,$s1,$p2,$s2)=@_;
+    return (6.*$t*$t-6.*$t) *$p1 + 5.*(3.*$t*$t-4.*$t+1.)*($s1-$p1)+
+           (-6.*$t*$t+6.*$t)*$p2 + 5.*(3.*$t*$t-2.*$t)   *($s2-$p2);
+ }
+ #
+ # d^2/dt^2(...)
+ #
+ sub d2dt2_cubic_hermite {
+    my ($t,$p1,$s1,$p2,$s2)=@_;
+    return (12.*$t-6.) *$p1 + 5.*(6.*$t-4.)*($s1-$p1)+
+           (-12.*$t+6.)*$p2 + 5.*(6.*$t-2.)*($s2-$p2);
+ }
+ #
+ # Implentation of <functionplotresponse>
+ #
  sub start_functionplotresponse {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;
    my $result='';