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atan hooks for atan2

From: Wolfgang Rupprecht
Subject: atan hooks for atan2
Date: Sat, 16 Feb 2002 13:44:19 -0800 (PST)

This patch adds hooks for calling atan2 if the lisp atan function is
invoked with 2 args.  This patch is necessary if one wants to use atan
to determine the compass direction of a positional shift given a
delta-X and delta-Y.  Without it, all answers are folded into the
range -pi/2, +pi/2.

(This patch is being released under the GPL, yada, yada, yada).


cd /usr/pkgsrc/editors/emacs/work/emacs-20.7/src/
diff -u /usr/pkgsrc/editors/emacs/work/emacs-20.7/src/floatfns.c.\~1\~ 
--- /usr/pkgsrc/editors/emacs/work/emacs-20.7/src/floatfns.c.~1~        Tue Apr 
14 05:29:27 1998
+++ /usr/pkgsrc/editors/emacs/work/emacs-20.7/src/floatfns.c    Sat Feb 16 
13:20:23 2002
@@ -256,13 +256,21 @@
   return make_float (d);
-DEFUN ("atan", Fatan, Satan, 1, 1, 0,
-  "Return the inverse tangent of ARG.")
-  (arg)
+DEFUN ("atan", Fatan, Satan, 1, 2, 0,
+       "Return the inverse tangent of Y_divided_by_X.\n\
+If second optional are is given, return the inverse tangent of Y and X")
+  (arg, arg2)
      register Lisp_Object arg;
   double d = extract_float (arg);
-  IN_FLOAT (d = atan (d), "atan", arg);
+  if (NILP (arg2))
+    IN_FLOAT (d = atan (d), "atan", arg);      
+  else
+    {
+      double d2 = extract_float (arg2);
+      IN_FLOAT2 (d = atan2 (d, d2), "atan", arg, arg2);
+    }
   return make_float (d);

Diff finished at Sat Feb 16 13:22:11

Wolfgang Rupprecht    <address@hidden>     http://www.wsrcc.com/wolfgang/
Coming soon: GPS mapping tools for Open Systems. http://www.gnomad-mapping.com/

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