Do I need a parser?

[Alan Meyer]

On 6/29/19 8:39 AM, josé mariano wrote:
> Dear all,
> 
> I'm sure that this subject has been addressed many times before on this forum, but my poor knowledge of English and of computer jargon and concepts results on not being able to find the answer i'm looking for when I search the forum.
> 
> So here is my problem: I have this open source project for the scientific community were i want to duplicate an old MS-DOS application written in Fortran. I don't have the source code. The idea is to re-write the software in Python. Originally, the old application would would need to input files: one config file, written with a specific format (see below) and a second one, the so-called scrip file, that defines the sequence of operations to be performed by the main software, also written in a specific format.
> 
> To make the transition to the new application as painless as possible to the users, because most of them have their collection of scrips (and settings) developed over the years and are not willing to learn a new script language, I would like to make the new app 100% compatible with the old input files.
> 
> The operation of the new software would be like this: From the shell, run "my_new_software old_script_file.***". The new software would load the old_script, parse it (?), set the internal variables, load the script and run it.
> 
> So, to get to my questions:
> 
> - To load and read the config file I need a parser, right? Is their a parser library where we can define the syntax of the language to use? Are there better (meaning easier) ways to accomplish the same result?
> 
> - For the interpretation of the script file, I don't have any clue how to this... One important thing, the script language admits some simple control flow statements like do-wile, again written using a specific sintax.
> 
> Thanks a lot for the help and sorry for the long post.
> 
> Mariano
> 
>    
> 
> Example of a config (settings) file
> ========================
> .....
> CONDAD     -11
> BURAD2     4 SALT1 1.0 KNO3
> ELEC5      -2.0 mV 400 58 0. 0
> .....
> 
> 
> Example of a script
> ===================
> !Conductivity titration
> cmnd bur1 f
> set vinit 100
> set endpt 2000
> set mvinc 20
> set drftim 1
> set rdcrit cond 0.5 per_min
> set dosinc bur1 0.02 1000
> set titdir up
> titratc cond bur1

I'll just add a general comment here.

Yes, you do need a parser and that parser should be a separate module or 
separate class from the rest of your program.  As Thomas Jollans wrote, 
str.split() might be enough to do all of the string twiddling for you.

If you have a separate class (or group of classes) that produces a 
configuration object and a script object then, if you discover examples 
of configuration or script files that you weren't aware of when you 
wrote the code, then may you only need to modify your parser code and 
may not have to modify your script execution logic.

Finally, I want to say that I wish everyone in the U.S. had as much 
command of English as you do.  Si pudiera hablar español tan bien como 
usted habla inglés, estaría muy feliz.  (You should have seen what that 
looked like before I applied Google Translate :)

    Alan