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FlightGear Newsletter July 2010: Difference between revisions
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"Nasal for newbies"
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Last month, the infamous [http://wiki.flightgear.org/index.php/Howto:_Get_rid_of_common_errors#Warning:_Picked_up_TriangleIntersect QNaN errors] that may cause FlightGear to become [[Showstoppers|unresponsive]] have been linked to potential issues in the Nasal interpreter (and more generally Nasal code) by flug, for more details please see: [http://www.flightgear.org/forums/viewtopic.php?f=18&t=8483&p=83701 "Nasal source of Dreaded Triangle Error-source of many probs?"]. | Last month, the infamous [http://wiki.flightgear.org/index.php/Howto:_Get_rid_of_common_errors#Warning:_Picked_up_TriangleIntersect QNaN errors] that may cause FlightGear to become [[Showstoppers|unresponsive]] have been linked to potential issues in the Nasal interpreter (and more generally Nasal code) by flug, for more details please see: [http://www.flightgear.org/forums/viewtopic.php?f=18&t=8483&p=83701 "Nasal source of Dreaded Triangle Error-source of many probs?"]. | ||
For the time being, you will want to look out for any Nasal code that contains unchecked divisions with unvalidated divisors. | For the time being, you will want to look out for any Nasal code that contains unchecked divisions with unvalidated divisors. | ||
== Nasal for newbies == | |||
[[Nasal]] is the name of FlightGear's built in scripting language that allows people to easily create custom logics for adjusting and driving FlightGear internals without having to modify the C++ source code or recompile FlightGear. | |||
To use Nasal you don't need to be a programmer, in fact Nasal is so simple that it can be used by people without any prior programming experience at all. Still Nasal is very powerful and flexible. | |||
Nasal scripts can be used for doing many interesting things. | |||
Some of the more recent examples being the bombable addon, the local weather system or the seeking AI missiles, all of which are purely implemented as Nasal scripts. | |||
You can see for yourself how easy it is to get started writing Nasal scripts: | |||
Just create a new plain text file (using an editor like notepad on Windows) named "hello.nas" in the $FG_ROOT/Nasal directory, paste the following contents: | |||
print("My first Nasal script !"); | |||
Watch the black shell window when starting FlightGear and you'll see the "My first Nasal script !" being printed to the console. | |||
As you have surely noticed, all Nasal scripts in the $FG_ROOT/Nasal directory get loaded and run automatically during FlightGear startup. | |||
The sample program just consists of one instruction, namely "print". Which is a function call to the built-in "print" function of the Nasal interpreter. | |||
The print function can not only print strings, but also numbers or individual characters. | |||
Function calls in Nasal always look like this: | |||
name(); | |||
Where "name" would be the function's Nasal name, and then parentheses contain all parameters that you want to pass to the function. The expression is terminated using a semicolon. | |||
To pass arguments to the function, you would simply add these in between the parentheses and separate them using a comma: | |||
print(100, 200, 300); | |||
==In the hangar== | ==In the hangar== | ||