GroovyShell and Category

gistfile1.groovy

shell = new GroovyShell()
shell.metaClass.invokeMethod = {String name, args ->
	def metaMethod = delegate.metaClass.getMetaMethod(name, args)
	def result
	switch (name) {
		case 'parse':
			result = metaMethod.invoke(delegate, args)
			def oldRun = result.metaClass.getMetaMethod('run')
			result.metaClass.run = { ->
				def result2
				def delcopy = delegate
				use(FormulaCategory) {
					result2 = oldRun.invoke(delcopy)
				}
				result2
			}
			break
			
		case 'evaluate':
			def delcopy = delegate
			use(FormulaCategory) {
				result = metaMethod.invoke(delcopy, args)
			}
			break
		default:
			result = metaMethod.invoke(delegate, args)
		}
		result
	}
}