How hard would it be to include support for { } and [ ]?

[Nicholaswogan]

Really useful package. Thanks. I'm considering trying to add support for flow style dictionaries and lists using {} and [] . I'm just wondering how hard this would be?

[jornbr]

Thanks for considering this - it has been on our wish list for a while. The starting point would be the read_value routine in yaml.F90, where you would determine whether the next character in the stream is a [ or {. That's similar to how block lists are detected and handled there:

fortran-yaml/yaml.F90

Line 166 in 2d20331

if (file%line(1:2)=='- ') then

(it then repeatedly calls "read_value" to read list elements).

However, the read_value routine will likely need to be updated then to (optionally) operate in flow (rather than block) mode, and stop reading a new value when a , is encountered. Doable but not entirely trivial. If you'd like to give it a go, great! We probably should also look into putting together a test suite of yaml files then, and verify for instance whether they survive read-dump-read round-tripping.

Cheers,

Jorn

[Nicholaswogan]

Thanks for the information! I might try to do this at some point in the next few weeks as I'm working on a project that depends on fortran-yaml.

[Nicholaswogan]

I gave it a try. I was able to do almost any nested list in flow style, but had some problems with the very end of the last nested list. I did not try to do dictionaries. My attempt is attached.

Overall, I just added two if statements to read_value. The first if statement was to identify "[", the beginning of a new list, and the second is to read the values within a list. I added attributes to type_file, for keeping track of where you are in nested lists, as the parsing occurs.

I don't love what I have done, but maybe the overall approach is along the right lines.

yaml.F90.zip

[Nicholaswogan]

@jornbr I used your type system with the parser in yaml-cpp to make a new package fortran-yaml-cpp. The API is nearly identical to fortran-yaml. But now it can deal with a flow style yaml.

[jornbr]

That seems a great way to get more robust yaml parsing while still preserving compatibility with the fortran-yaml interfaces. That could be useful for my own applications too, particularly if the underlying C++ code is not too particular about compilers. I'll hope to take a close look soon.

[Nicholaswogan]

I've tested the following two C++ and Fortran compiler combinations on MacOS. They both seem to work. I'll get around to testing other compiler combinations and OSs at some point.

• Fortran compiler = GNU 11.2.0 and C++ compiler = AppleClang 12.0.5.12050022
• Fortran compiler = GNU 11.2.0 and C++ compiler = GNU 11.2.0

[Nicholaswogan]

@jornbr I am new to Licenses. What license should I put on fortran-yaml-cpp, so it does not violate fortran-yaml license. I also have another project which depend on fortran-yaml which I'm going to publish really soon. I want to use the proper license.