# Conditionals for Pure Data: Interactive tutorial

Computer programs need to determine how to proceed at certain points in their program flow, depending on whether certain predetermined (or variable) conditions have been met or not. Such operations are a mainstay of computing and are known as a “conditional” test. For example, when a condition has been met, a result of TRUE (“1”) is produced, otherwise a FALSE (“0”) message results: these are known as Boolean values. Conditional tests (or conditionals for short) are particularly useful in programs such as “generative” music compositions, where the “rules of the game” are predetermined, and require no further input from the programmer after the piece has started.

The conditionals provided in Pure Data (Pd) are very basic, consisting of simple relational operators (such as == [“equals”], != [“not equals”], <, <=, >,  >=) and logical operators ( && [“and”],  || [“or”]). In order to make your own conditional objects that match the complexity of what Max/MSP offers as standard, you’ll need to have a look at the 9 (interactive) examples illustrated above. By changing the values in the yellow boxes, each test will produce one of two possible outcomes.

Whereas Pd’s relational and logical operators produce Boolean values, a “Select” object is necessary in order to produce a “bang” result (which is often necessary when programming in Pd). In the examples provided, the select object has been used to produce either a bang (only if a TRUE value results) or two different bangs (one for TRUE and another for FALSE).

Click here to download the interactive tutorial. Please note, you’ll first need to have Pure Data (Pd) installed on your computer to use this app (it’s free). Once you understand how each of the provided complex conditionals work, you can then embed them in their own subpatches, making your patcher window much less cluttered (as illustrated in the orange square next to example 1. Click on the pd X==Y object to see “inside”). In order to get more information on what each discreet Pd object can do control+click (Apple users*) on the relevant object. Enjoy.

The downloadable interactive tutorial is (cc) 2016 Marshall Heiser (Attribution 4.0 International). This license lets you distribute, remix, tweak, and build upon my work, even commercially, as long as you credit me for the original creation. Any derivatives will also allow commercial use. Click here for more licence details.