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I am not sure if this is so much a readme as it is notes, thoughts, and a place to store research. I may in the future start a project wiki to house all this stuff but for now this is my quick and dirty solution.
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This is an ongoing project to help me learn how to write an interperter. This is a daunting task for someone with no real CS background. I have a tenuious grasp of grammers and how that helps to define a language.
I don't really want to read a whole book on language theory and Turing machines. I want a working knowledge and maybe someday a theoretical knowledge.
The end goal of this project is a very flexible way to accept text file input from users. I think it is possible to write a "language" for an analysis program that the user can learn. I think this can be very powerful, flexible, scalable, and efficient way to accept user input via a text file. It's not a glamorous and shining as a GUI but it does the job much better in my opinion.
GUIs are great for some programs but in my experience with engineering analysis and design, program users want very good control over what the program is doing. How do you offer that control? Basically provide them an API of commands to run the program as they see fit. You can build in functions and tools that offer an expedited way to set up the model/geometry/analysis but it is up to the user to use that function or tool. You also have to provide them a guide about what has to be defined and in what order for the program to run properly, e.g. you can't call function bar without first defining parameter foo.
I have considered writing a text parser with regex but I think that there will be some limitations. I may come back to this idea because I think there has to be some kind of "lexer" and I may have to write something like this. I think the limitations I am considering focus mainly around the flexibility. If I want to implement a new function or parameter I have to re-write or add to the already complex regex. The regex will have to include all the keywords to be able to break the input file apart which is inherently not a flexible solution. You are hard-coding keywords into the program, generally not a good solution.
Links:
http://compilers.iecc.com/crenshaw/tutor2.txt
http://forums.devshed.com/programming-languages-139/interpreter-compiler-312483.html#post1342279
https://learnpythonthehardway.org/book/ex48.html