[genius] Fri Mar 10 13:15:25 2017 Jiri (George) Lebl <jirka 5z com>

[George Lebl <jirka src gnome org>]

commit 0246a972d31428d816862034b7e7ee1183a1e55a
Author: Jiri (George) Lebl <jiri lebl gmail com>
Date:   Fri Mar 10 13:15:42 2017 -0600

    Fri Mar 10 13:15:25 2017  Jiri (George) Lebl <jirka 5z com>
    
        * examples/dalemb-pulse.gel: Add some other example functions
          (commented out) for playing around.

 ChangeLog                 |    5 ++++
 examples/dalemb-pulse.gel |   49 +++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 52 insertions(+), 2 deletions(-)
---
diff --git a/ChangeLog b/ChangeLog
index 7a6ca65..57044ff 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Fri Mar 10 13:15:25 2017  Jiri (George) Lebl <jirka 5z com>
+
+       * examples/dalemb-pulse.gel: Add some other example functions
+         (commented out) for playing around.
+
 Wed Feb 15 13:13:40 2017  Jiri (George) Lebl <jirka 5z com>
 
        * examples/fourier-series-*.gel: Run 10 instead of 3 iterations of
diff --git a/examples/dalemb-pulse.gel b/examples/dalemb-pulse.gel
index e5afc2d..d849ec7 100644
--- a/examples/dalemb-pulse.gel
+++ b/examples/dalemb-pulse.gel
@@ -2,14 +2,15 @@
 # Name: D'Alembers solution animation of a plucked string
 
 #
-# Solution to the wave equation
+# Solution to the wave equation u_tt = u_xx
 # The initial conditions are: position at F(x) and velocity at 0
+# Boundary conditions are u(0,t) = u(1,t) = 0
 #
 
 # A pulse function.  Feel free to set this function to whatever you want,
 # though you should have ends at 0
 function F(x) = (
-    # This makes the functions periodic
+       # This makes the functions periodic
        while x < -1 do x = x + 2;
        while x > 1 do x = x - 2;
        
@@ -25,6 +26,50 @@ function F(x) = (
        )       
 );
 
+# A plucked string function.
+function F(x) = (
+       # This makes the functions periodic
+       while x < -1 do x = x + 2;
+       while x > 1 do x = x - 2;
+       
+       if x < 0 then -F(-x)
+       else if x < 0.5 then x
+       else 1-x        
+);
+
+# A plucked string function in two places.
+#function F(x) = (
+#      # This makes the functions periodic
+#      while x < -1 do x = x + 2;
+#      while x > 1 do x = x - 2;
+#      
+#      if x < 0 then -F(-x)
+#      else if x < 0.25 then -x
+#      else if x < 0.5 then x-0.5
+#      else if x < 0.75 then x-0.5
+#      else 1-x        
+#);
+
+
+# A plucked string in two places both in positive directions.
+#function F(x) = (
+#      # This makes the functions periodic
+#      while x < -1 do x = x + 2;
+#      while x > 1 do x = x - 2;
+#      
+#      if x < 0 then -F(-x)
+#      else if x < 0.25 then x
+#      else if x < 0.5 then 0.5-x
+#      else if x < 0.75 then x-0.5
+#      else 1-x        
+#);
+
+# Examples of superposition of sin waves
+#function F(x) = (1/2)*sin(2*pi*x);
+#function F(x) = (1/2)*sin(2*pi*x) + (1/3)*sin(7*pi*x);
+#function F(x) = (1/2)*sin(2*pi*x) + (1/3)*sin(7*pi*x) + (1/8)*sin(20*pi*x);
+
+
 #t a paramater
 function yy(x) = (F(x-t) + F(x+t))/2;