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187 lines
8.6 KiB
Markdown
| [Home](/trick) → Frequently Asked Questions (FAQ) |
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# Appendix
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01. [What is Trick?](#whatistrick)
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01. [Why should I use Trick?](#whyshouldiusetrick)
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01. [What operating systems can Trick run on?](#whatoperatingsystemcantrickrunon)
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01. [Does Trick run on Windows?](#doestrickrunonwindows)
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01. [Which MacOSX package manager works best with Trick?](#whichmacosxpackagemanagerworksbestwithtrick)
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01. [What is the current version of Trick?](#whatisthecurrentversionoftrick)
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01. [What are the differences between Trick versions?](#whatarethedifferencesbetweentrickversions)
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01. [Can Trick interact with other applications?](#cantrickinteractwithotherapplications)
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01. [Does Trick work with MATLAB/Simulink?](#matlabsimulink)
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01. [Does Trick work with Core Flight Software (CFS)?](#coreflightsoftware)
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01. [I found a bug with Trick, how do I tell someone?](#ifoundabugwithtrickhowdoitellsomeone)
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01. [I have a question about Trick, where should I ask it?](#ihaveaquestionabouttrickwhereshouldiaskit)
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01. [Why won't my Trick simulation compile?](#whywontmytricksimulationcompile)
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01. [What units can Trick use?](#whatunitscantrickuse)
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01. [Do I need internet access to build Trick?](#doineedinternetaccesstobuildtrick)
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01. [Can I access class protected/private variables?](#caniaccessclassprotectedprivatevariables)
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01. [Are there faster ways to implement events?](#aretherefasterwaystoimplementevents)
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01. [Are there input file template limitations?](#arethereinputfiletemplatelimitations)
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01. [Is Trick gluten-free, grass-fed, organic, non-GMO, environmentally conservative, free-range, vegan, and dolphin safe?](#istrickgfgfongmoecfrvads)
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---
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<a name="whatistrick"></a>
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## What is Trick?
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Trick is a simulation environment and toolkit that allows users to create complex physics simulations.
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<a name="whyshouldiusetrick"></a>
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## Why should I use Trick?
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You should use Trick if you want to develop an accurate physics simulation without needing to develop core simulation capabilities manually.
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<a name="whatoperatingsystemcantrickrunon"></a>
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## What operating systems can Trick run on?
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Trick currently runs on all System V and POSIX compliant UNIX operating systems. MacOSX and most Linux distributions fall under this umbrella.
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<a name="doestrickrunonwindows"></a>
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### Does Trick run on Windows?
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Trick does not run natively on Windows, however it *is* possible to run Trick on the Windows 10 Linux Subsystem. Trick will not be ported to Windows until Windows is POSIX compliant, which is highly unlikely.
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<a name="whichmacosxpackagemanagerworksbestwithtrick"></a>
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### Which MacOSX package manager works best with Trick?
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Homebrew.
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<a name="whatisthecurrentversionoftrick"></a>
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## What is the current version of Trick?
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Trick 19 is the version currently being developed on GitHub. We also maintain a branch for Trick 15 and Trick 17.
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<a name="whatarethedifferencesbetweentrickversions"></a>
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### What are the differences between Trick versions?
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Trick 15 marked the first iteration of an open source Trick Simulation Environment. Trick 17 has several bug fixes, new features, and is currently in active development; it should be used for all new simulation development.
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<a name="cantrickinteractwithotherapplications"></a>
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## Can Trick interact with other applications?
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Trick is capable of interacting with other applications via the variable server; the variable server contains the values of a simulation which can then be sent over TCP/IP to a client application.
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<a name="matlabsimulink"></a>
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### MATLAB/Simulink
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MathWorks developed a package to generate Trick friendly code from their models. An introduction video on Trick-MATLAB/Simulink interfacing can be found [here.](http://www.mathworks.com/videos/connecting-simulink-with-other-simulation-frameworks-86546.html)
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<a name="coreflightsoftware"></a>
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### Core Flight Software (CFS)
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cFS support for Trick is provided by the following external projects:
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* [TVS-IO](https://github.com/nasa/tvsio) is an open-source, Core Flight Software (cFS) application that provides for two-way communication between a **cFS** Software Bus Network (SBN) and a Trick simulation.
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* Another soon to be released capability, presumably called TrickCFS should also be available soon as open-source software. Stay-tuned.
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<a name="ifoundabugwithtrickhowdoitellsomeone"></a>
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## I found a bug with Trick, how do I tell someone?
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Create an issue on GitHub [here](https://github.com/nasa/trick/issues/new). The more descriptive you are, the faster we can solve the issue.
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<a name="ihaveaquestionabouttrickwhereshouldiaskit"></a>
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## I have a question about Trick, where should I ask it?
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Create an issue on GitHub [here](https://github.com/nasa/trick/issues/new) with "QUESTION: " appended to the title.
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<a name="whywontmytricksimulationcompile"></a>
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## Why won't my Trick simulation compile?
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There are many reasons why a simulation will fail to compile properly.
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01. Trick can't find your header files or source code.
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02. You haven't properly set your environmental variables.
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03. You haven't properly installed all required dependencies.
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<a name="whatunitscantrickuse"></a>
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## What units can Trick use?
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Trick is capable of utilizing the vast majority of imperial and metric units. Trick uses the UDUNITS C library/database in its unit calculations. For a list of the most common units, run **trick-units** in a terminal window after installing Trick.
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<a name="doineedinternetaccesstobuildtrick"></a>
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## Do I need internet access to build Trick?
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Trick's Java GUIs rely on several 3rd party .jar files which are normally downloaded during the initial compilation of Trick. If you are compiling on a machine without internet access you may copy the directory ${TRICK\_HOME}/libexec/trick/java/lib to a machine that does have internet access and run make on that machine.
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<a name="caniaccessclassprotectedprivatevariables"></a>
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## Can I access class protected/private variables?
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If the Trick memory manager and init attribute function is made a friend of a class, we are able to access protected/private variables in the input file through the memory manager.
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```c++
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class A {
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// This class triggers Trick to process protected/private variables
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friend class InputProcessor ;
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// This friend function follows this naming convention "void init_attr ## <class_name>()"
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friend void init_attrA() ;
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private:
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int ii ;
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} ;
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```
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Input File statements
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```python
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# Direct access will fail
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my_sim_object.a.ii = 1 #fails
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var = my_sim_object.a.ii #fails
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# Use the var_set and var_get commands to access protected/private variables
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trick.var_set("my_sim_object.a.ii", 1)
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var = trick.var_get("my_sim_object.a.ii")
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```
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<a name="aretherefasterwaystoimplementevents"></a>
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## Are there faster ways to implement events?
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Trick has a few alternatives to an input file event. Both method execute faster than a regular input processor event, but are not as flexible.
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01. [A Just in Time (JIT) input file](/trick/documentation/simulation_capabilities/JIT-Input-Processor.html) is C++ code that is
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compiled and run during simulation execution.
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02. [Realtime Injection](/trick/documentation/simulation_capabilities/Realtime-Injector.html) stages variable assignments and executes them in bulk at the top of a software frame.
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<a name="arethereinputfiletemplatelimitations"></a>
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## Are there input file template limitations?
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Trick input files understand a lot about templates, but there is a limitation when using them. Input files cannot access a fixed array of template types directly. There are memory manager calls accessible from the input file that may be used to to read and write arrayed templates.
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```c++
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template < typename T > class A {
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public:
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T t;
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} ;
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class B {
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public:
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A<double> a[4] ;
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} ;
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```
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Here is an input file accessing the template type
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```python
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# direct access to arrayed template class will fail
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my_sim_object.b.a[1].t = 1 # fails
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var = my_sim_object.b.a[1].t = 2 # fails
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# use these memory manager calls instead
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trick.var_set("my_sim_object.b.a[1].t", 1)
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var = trick.var_get("my_sim_object.b.a[1].t")
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```
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<a name="istrickgfgfongmoecfrvads"></a>
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## Is Trick gluten-free, grass-fed, organic, non-GMO, environmentally conservative, free-range, vegan, and dolphin safe?
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Trick is composed entirely of information. It contains no matter, organic or otherwise. Therefore Trick contains no gluten,
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GMOs, nor is it fed by grass, vegetables, or meat. Trick could be described as environmentally conservative in that it runs on numerous POSIX (Unix-like) operating systems. Trick is of course free-range! It's Opensource!, and freely available to anyone, even dolphins with internet access.
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