Update theory and API docs with correct dihedral range.

docs-source/usersguide/theory.rst

@@ -920,7 +920,8 @@ of four particles.  That is, the interaction energy of each bond is given by
 
 where *f*\ (\ *...*\ ) is a user defined mathematical expression.  It may
 depend on an arbitrary set of positions {\ :math:`x_i`\ }, distances {\ :math:`r_i`\ },
-angles {\ :math:`\theta_i`\ }, and dihedral angles {\ :math:`\phi_i`\ }.
+angles {\ :math:`\theta_i`\ }, and dihedral angles {\ :math:`\phi_i`\ }
+guaranteed to be in the range [-π, π]. 
 
 Each distance, angle, or dihedral is defined by specifying a sequence of
 particles chosen from among the particles that make up the bond.  A distance

openmmapi/include/openmm/CustomCompoundBondForce.h

@@ -57,7 +57,8 @@ namespace OpenMM {
  * <li>distance(p1, p2): the distance between particles p1 and p2 (where "p1" and "p2" may be replaced by the names
  * of whichever particles you want to calculate the distance between).</li>
  * <li>angle(p1, p2, p3): the angle formed by the three specified particles.</li>
- * <li>dihedral(p1, p2, p3, p4): the dihedral angle formed by the four specified particles, in radians, on the domain [-pi,+pi).</li>
+ * <li>dihedral(p1, p2, p3, p4): the dihedral angle formed by the four specified particles, in radians, guaranteed
+ *     to be in the range [-pi,+pi].</li>
  * </ul>
  *
  * The expression also may involve tabulated functions, and may depend on arbitrary

openmmapi/include/openmm/CustomTorsionForce.h

@@ -70,8 +70,8 @@ namespace OpenMM {
  *
  * Expressions may involve the operators + (add), - (subtract), * (multiply), / (divide), and ^ (power), and the following
  * functions: sqrt, exp, log, sin, cos, sec, csc, tan, cot, asin, acos, atan, sinh, cosh, tanh, erf, erfc, min, max, abs, floor, ceil, step, delta, select.
- * All trigonometric functions are defined in radians, with the torsion `theta` on the domain [-pi, +pi), and log is the natural logarithm.
- * step(x) = 0 if x is less than 0, 1 otherwise.  delta(x) = 1 if x is 0, 0 otherwise.
+ * All trigonometric functions are defined in radians, with the torsion `theta` guranteed to be in the range [-pi,+pi].
+ * log is the natural logarithm. step(x) = 0 if x is less than 0, 1 otherwise.  delta(x) = 1 if x is 0, 0 otherwise.
  * select(x,y,z) = z if x = 0, y otherwise.
  */