Hadrian Basic Use

Before you begin...

Download any pre-built Hadrian JAR (except for the hadrian-gae WAR). This article was tested with Hadrian 0.7.1; newer versions should work with no modification. Scala >= 2.10 is required.

Launch a Scala prompt using that JAR as a classpath:

> scala -cp hadrian-standalone-TRUNK-jar-with-dependencies.jar

and import com.opendatagroup.hadrian.jvmcompiler.PFAEngine:

Welcome to Scala version 2.10.5 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_45).
Type in expressions to have them evaluated.
Type :help for more information.

scala> import com.opendatagroup.hadrian.jvmcompiler.PFAEngine

Simplest possible scoring engines

Let's start with an engine that merely adds 10 to each input. That's something we can write inline.

scala> val engine = PFAEngine.fromJson("""
     | {"input": "double",
     |  "output": "double",
     |  "action": {"+": ["input", 100]}}
     | """).head
engine: com.opendatagroup.hadrian.jvmcompiler.PFAEngine[AnyRef,AnyRef] = PFA_Engine_1@3f792b9b