Create your own language DESIGN -> PARSE -> INTERPRET

Language design Ask following questions before you start doing anything  What is the purpose of the language?  Why do we need it?  What exactly it should do? (how does it help to solve the problem?)  Who should use this language?  Is there some existing language that could help us to solve our problem?

Why do we ask such questions?

Language design: rule #1 1st rule of language design : keep it SIMPLE!  Easier to parse  Steep learning curve of the language  Code is more readable/strict  Code/program execution may be faster

Language design: rule #2 2nd rule of language design : keep it SIMPLE!!!

Config Template language WinCC OA project Config file/s Config file -sections Config file - properties

Config Template language  We have lots of WinCC OA projects  Each project has configuration file/s  Each “config” file has 1..* sections  Each section has 1..* properties  Each property has 1..* values  Template language is a tool that allows as to ask computer questions about config files. Are all the sections and properties correct?

How can we ask computer such questions? – REGexprs?  ?:\r\n)?[\t]))*"(?:(?:\r\n)?[\t])*)*\ ]))*"(?:(?:\r\n)?[\t])*)*\ ?:(?:\r\n)?[\t])*))*)?;\s*)

Config Template example '''print(“Hello World template!”);''' [general] {exactlyOnce} pvss_path = "C:/Siemens/" || "/opt/Siemens" proj_path = ''(value.toLowerCase().startsWith("c:/projects/"))'' [ui] showActiveShapes = 0 checkADAuthIntervall = >= 60

Root rule Section ruleProperty ruleValue/s rule Properties collection rule JS rule Sections collection rule JS rule

How to parse languages?

Interpreting language  Bytecode interpreters  Highly optimized machine independent code (Java/.NET/Emacs Lisp)  Abstract Syntax Tree interpreters  Keeps relations between statements  Allows to perform better analysis during runtime  Just-in-time compilation  Some representation of program is compiled to native code at runtime  Self-interpreter

Config files Parse config files Template Parse template Execute Execute template file Result Stack trace of failed rules

Template file Template model Exe. model Config file 01Config model Abstract model (JSON) Config file 02Config model Abstract model (JSON) Config file 03Config model Abstract model (JSON) Config file …Config model Abstract model (JSON) Config file xxConfig model Abstract model (JSON) … …

Config 01 Thread 1 Config 02 Thread 2 Config … Thread … Config xx Thread T Shared Template engine

How language design influences its execution? A LOT

Config 01 Thread 1 Config 02 Thread 2 Config … Thread … Config xx Thread T Shared Template engine

Interpreting parts of AST with JavaScript NashornJavaScript Config template “Template engine”AST Virtual machine JVMbytecode Hardware CPUassembler