ANTLR quickstart

He's a resource I wrote for those of you wanted to get started with ANTLR, but cut through the BS red tape and get straight to writing grammars! Here it is:

I spent a lot of time trying to get ANTLR in usable shape, and I found the documentation dreadful. So allow me to lay out a much easier alternative to using ANTLR right out of the box, that doesn't require finnicking with system variables that never work.

This may not be the most "flexible" route, but is certainly the quickest one in my experience. The instructions are usable in both UNIX and Windows.

1. Download the java jdk.After you have it installed you *should* be able to invoke the "java" command from your command prompt. test it using "java -version". If you get some kind of output from that, then great!
2. Download the ANTLR complete jar.There are two antlr sites in an attempt to separate ANTLR3 from ANTLR4.
   If you want ANTLR4, go to antlr.org
   If you want ANTLR3, go to antlr3.org
   In either case, download the complete jar to a location you wouldn't mind using it.
3. Test installationIn your command prompt move to the directory that contains the complete jar.
   try the command
   
   java -cp antlr-x.y.z-complete.jar org.antlr.Tool
   
   in ANTLR3, or in ANTLR4,
   
   java -cp antlr-x.y.z-complete.jar org.antlr.v4.Tool
   
   This command should work, and return options for ANTLR.
   The cp argument means you can you specify CLASSPATH within the command, removing
   the additional step of fooling around with system variables.
   
   
4. Test output
   Use the included "Exp.g" grammar taken from a stackoverflow question and run the following command in ANTLR3
   
   java -cp antlr-x.y.z-complete.jar org.antlr.Tool Exp.g
   
   or in ANTLR4
   
   java -cp antlr-x.y.z-complete.jar org.antlr.v4.Tool Exp.g
   
   If you're using your own grammar, make sure that the filename matches the first line, e.g. grammar css = css.g
   
   
5. Test different target.In your grammar, add the line
   
   options{language = C;}
   
   where "C" is whatever target language you'd want. I'm typically concerned with C or C++
   output, so I use "C" or "Cpp", though ANTLR4 doesn't target C or CPP.
   Run the same command again, and check that it ran correctly and output matches the desired filetype.
   
   
6. Design your grammar
   Congratulations. If the step before worked, than you have everything you need to start doing *actual work* with ANTLR! I hope this was helpful in getting you started, and not hung up on installing stuff. 

Edit:
I found myself also need to check out antlrworks to see how my grammar is structured. As of 1.5.2, try

java -jar antlrworks-1.5.2-complete.jar org.antlr.Tool <grammar.g>


"Installing things is the hardest part of programming."

Useful Tips From My First Week Of Prolog:

1. Understanding how Prolog works is paradigm. Unlike other procedural languages, Prolog is seeking to set things equal, or unify them. This a much more intelligent behavior that characterizes it as a “fifth-generation language”. The philosophy of the fifth-generation languages is to attempt to “describe” the problem to Prolog as opposed to just writing it out. Take that with a grain of salt though. It will make sense as you develop more and more advanced programs.
   
2. Prolog is pretty bare bones in that you have to write a lot of basic features yourself, and you also have limited tools at your disposal for debugging. One of the tools you need to take advantage of is the trace function. This allows you incite to the complex control flow of Prolog’s stack. However, do not get too caught up in what it’s trying to do, but instead focus on what is being called, and watch diligently for failures.
   
3. When making accumulator-style predicates, try to include an extra argument, as it will make writing a base case a lot easier. Here’s a simple example of an accumulator-style length predicate, len, that calls on a predicate accLen to accomplish the task:
   
   accLen([_|T],A,L)  :-
   Anew  is  A+1,  
   accLen(T,Anew,L).
   accLen([],A,A).    
   len(List,Length)  :-  accLen(List,0,Length).
   
4. If you have a problem where prolog seems to want to “redo” one of your predicates to find another unification, you can use the symbol ! to denote no redos. This will be most helpful in your base case.
   
5. Prolog has a sort of “not” operator, but it can be hard to find in the documentation or in a google search (unless you sold out to SWI-prolog). By using \+ we signify that the predicate is true if it fails.
   
   For example,
   \+ member(x, List).
   
   Is only true if x is not in the list.