Logic

Booleans

Numeric variables can store a whole range of different numbers. Boolean variables can only store two values referred to as Yes or No, True or False, 1 or 0. Obviously we never use booleans to perform calculations because of their limited range. We use booleans to evaluate conditions.

Icon	Name	Syntax	Inputs	Outputs
	Boolean	--	True/False Radio Button	Boolean

The boolean Node in Dynamo is a basic radio button, toggling between true and false.

At the most basic level, Dynamo has a boolean Node which functions as a light switch for logical operations. This is a fundamental element for making conditional evaluation.

"If"

The "If" statement is a key concept in programming: "If this is true, then that happens, otherwise something else happens. The statement's decision is driven by a boolean, and the two results are defined by the user. There are multiple ways to define an "If" statement in Dynamo:

Name	Syntax	Inputs	Outputs
If	If	test, true, false	result
Formula	IF(x,y,z)	x, y, z	result
Code Block	(x?y:z)	x, y, z	result

Let's go over a brief example on each of these three nodes in action using the conditional "If" statement:

In this image, the boolean is set to true, which means that the result is a string reading: "this is the result if true". The three Nodes creating the If statement are working identically here.

Again, the Nodes are working identically. If the boolean is changed to false, our result is the number Pi, as defined in the original If statement.

Relational Operators

Name	Syntax	Inputs	Outputs
Less Than	<	x,y	boolean(s)
Less Than or Equal To	<=	x, y	boolean(s)
Greater Than	>	x, y	boolean(s)
Greater Than or Equal To	>=	x, y	boolean(s)
Equal To	==	x, y	boolean(s)
Not Equal To	!=	x	boolean(s)

Relational operators receive one or more inputs, and output a boolean depending on the result of a specific test. In summary, these are the "greater than, less than" tests. The demo below gives us an example.

The result of each test is a boolean. In the less than test, 2 is indeed less than 5, o the result is true. In the greater than test, 2 is not greater than 5, so the result is false.

Logic Gates

Name	Syntax	Inputs	Outputs
And	&&	x, y	boolean(s)
And	And	bool0,bool1...	boolean(s)
Or	//	x, y	boolean(s)
Or	Or	bool0, bool1...	boolean(s)
Xor	Logic.Xor	a, b	boolean(s)
Not	Not	x	boolean(s)

In its simplest form, a logic gate receives two booleans and outputs one boolean. These are based on fundamental sets, much like a Venn Diagram. Dynamo uses the basic gates of And, Or, and Xor.

And/&& - In the table above, the two Nodes for And may be confusing. Here is how they're different:

The && Node receives two inputs. The And Node receives two inputs by default (middle icon), but one can click the +/- to add or subtract more inputs (right icon with 4 inputs). Other than that, the two are functionally identical. So go with And Node.

Xor - This Node returns a true value if and only if one of the values is true.

This image show the four combinations of two booleans. If both values are true, a false is returned. If both values are false, a false is also returned. The true value is return if and only if one of the values is true. This rounds out the three main logic gates for two booleans.

Filter

Icon	Name	Syntax	Inputs	Outputs
	Filter By Boolean Mask	List.FilterByBoolMask	list, mask	in, out

List.FilterByBoolMask is a great tool for geometry operations. After conducting a conditional test on an array of elements, one can parse through those elements with this node. In the exercise below, we demonstrate this in detail.

logic