# Predicates - avram - a virtual machine code interpreter
avram - a virtual machine code interpreter

#### 2.7.11 Predicates

A couple of operations are built into the virtual machine for performing tests efficiently. These functions return either `nil` for false or `(nil,nil)` for true, and are useful for example as a predicate p in programs of the form `conditional(`p`,(`f`,`g`))` among other things. In this example, the predicate is applied to the argument, a result of `(nil,nil)` causes f to be applied to it, and a result of `nil` causes g to be applied to it.