Update ChLinkSpring to use ChSharedPtr to handle ChFunctions.
Fix bugs in copying ChFunction member variables
Update ChLinkEngine to use ChSharedPtr to handle ChFunctions.
Add functions to return the spring length and velocity.
Add ChLinkSpringCB, a spring-damper element based on a user-provided functor for force evaluation.
Add function to return the current deformation of a ChLinkSpringCB
New operators for doing transformations with mixed types ChFrame / ChFrameMoving. This was not possible explicitly in previous API and forced to promote a ChFrame to a ChFrameMoving by constructing it before doing the * or >> operation with a ChFrameMoving.
This is implemented now for both  * operator (right to left coord. transformation) and >> operator (left to right transformation).
Note that when doing  ChFrame * ChFrameMoving one could have the option of implementing either ChFrame  or ChFrameMoving as return type. I decided to return the type 'at the end' of the kinematic transformation, that is the right most in the * expressions and the leftmost in the >> expressions, so I decided that  ChFrame * ChFrameMoving  returns a ChFrameMoving , whereas  ChFrameMoving *  ChFrame  returns a ChFrame.  In most cases this fits the needs of the programmer and does not introduce too overhead as returning always the more complex type ChFrameMoving.
In future I'll add also mixed operators for ChCoordsys vs ChFrame  and ChFrameMoving.
Merge branch 'develop' of https://github.com/projectchrono/chrono into develop
Fixing bugs in new ChFrameMoving code - GCC compatibility and such.
New feature: control the flow in kg/s (mass per second) optionally, in alternative to default particle/second
New feature: enable a limit for the max amount of mass to be created.
Fix compilation issues for clang 5.1 on osx
Merge branch 'develop' of https://github.com/projectchrono/chrono into develop
Move using namespace std after using namespace chrono.
Clang gets confused and isn't sure if it's referring to std::chrono or chrono::
This is only an issue because of c++11
Fixed int/double confusion in mass reservoir of particle emitter
Merge branch 'develop' of https://github.com/projectchrono/chrono into develop
Improvements on flow control accessors
New feature: the ChRandomShapeCreatorFromFamilies can define the percentuals of the families in terms of created mass, in alternative to the default percentuals on number of created particles.
This is especially useful because in many cases, granulometry data is provided in terms of masses, for particle types, and this is not easily related to the amount of particles, especially if each family has different distributions for random sizes, shapes, etc.
Fix a potential bug with iterators. If the particle event is of type ChParticleProcessEventRemove, the iterator in the previous implementation would be invalidated during the iteration, and might create random segfaults.
Improved emitter demos.
Added * and >> operators also for ChCoordsys objects. They work in the same way as they work in the ChFrame class.
Also, added the *= and >>= operators, for in-place transformations (concatenations of transformations)