A to Z Scripting: Basic maths

Basic maths symbols

You can use basic maths symbols, as well as brackets (parentheses):

symbol	effect	can be used with
+	add/combine	floats, vectors, strings
-	subtract	floats, vectors
*	multiply	floats
/	divide	floats

The = sign

An important difference is what the = sign does. In scripting, = means "set", while == means "equals".

teleport_destination	= '20 20 20';		//set teleport_destination to '20 20 20'
float1 			= float2 + float3;	//set float1 to the sum of float2 and float3
if ( float1 == float2 )				//check if float1 is equal to float2

== is used in conditionals to check whether a condition is true (2 values are equal to each other) before carrying out an associated set of instructions. That's described in detail in a later article, A to Z Scripting: Conditionals.

The = sign can be combined with a maths symbol. Both the lines below do the exact same thing:

float1	= float1 + float2;	//set float1 to: current value + float2
float1	+= float2;		//set float1 to: current value + float2

Increasing/decreasing

Increasing (incrementing) a variable's value by 1 would work like this:

counter = counter + 1;		//set "counter" to: the current value of "counter" + 1
counter += 1;			//set "counter" to: the current value of "counter" + 1

An alternative method to increase or decrease a variable by 1 is:

counter++;			//increase "counter" by 1
counter--;			//decrease "counter" by 1

Be aware that the alternative "prefix" forms of these - found in the C language - are not supported:

++counter;			// not legal
--counter;			// not legal

Combining

You can freely combine script events, variables and absolute values in one line like this:

teleport_destination = $player1.getOrigin() + teleportation_offset + '0 0 16';

Strings can be cobbled together from strings, floats and vectors with the + sign. If you also want to include entities you need to turn them into strings with getName(). This is quite useful for sending helpful messages to the console while testing the script:

sys.println(entity1.getName() + " is at the location " + entity1.getOrigin());	//+ doesn't work with entities, so you need to use getName() to turn it into a string

What you can't do is perform maths operations with both floats and vectors. You'll need to i.e. use a script event to convert the vector into a float (see "Vectors").

Integers

There's no data type for integers in DoomScript, but you can make an integer out of a float like this:

float integer1 = int(5.8);	//returns 5

int() is a utility script, you can read more about them here: A to Z Scripting: Utility scripts.

Vectors

You can add or subtract vectors from each other. Things like multiplication or turning a vector into a distance require script events such as DotProduct(), CrossProduct() and vecLength().

You can access & change individual components of a vector variable by appending _x, _y or _z to the name, i.e. teleport_destination_z. These will be floats.

More detail on vector maths and what you can do with it in A to Z Scripting: Special methods.

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• Next article: A to Z Scripting: Setting up the .script files
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