feature_2225_level_string_with_at

[hsoh-u]

Expected Differences

The level string (begins with @) is applied as the value only.
The current implementation two more steps and they are disabled

1. with @: if the value does not exist: apply the value as offset. For example, MET is looking for the value "29" first with @29. If there is no matching value and the dimension is greater than 29, MET applies 29 as offset.
2. without @: if the offset is out of range (a negative value or bigger than dimension), it's applied as value. For example, (2000,,), If the dimension is less than 2000, MET finds the level with value 2000.

• Do these changes introduce new tools, command line arguments, or configuration file options? [No]
  
  If yes, please describe:
  

• Do these changes modify the structure of existing or add new output data types (e.g. statistic line types or NetCDF variables)? [ No]
  
  If yes, please describe:
  

Pull Request Testing

• Describe testing already performed for these changes:
  

The following tests should fail:

./plot_data_plane /d1/personal/hsoh/data/MET-1815/gfs_2012040900_F012.nc plot.ps 'name="PRES_4_PVL"; level="(2000,*,*)"; file_type=NETCDF_NCCF;' -v 4
./plot_data_plane /d1/personal/hsoh/data/MET-1815/gfs_2012040900_F012.nc plot.ps 'name="PRES_4_PVL"; level="(@1,*,*)"; file_type=NETCDF_NCCF;' -v 4

• Recommend testing for the reviewer(s) to perform, including the location of input datasets, and any additional instructions:
  

• Do these changes include sufficient documentation updates, ensuring that no errors or warnings exist in the build of the documentation? [No]

• Do these changes include sufficient testing updates? [No]

• Will this PR result in changes to the test suite? [No]
  
  If yes, describe the new output and/or changes to the existing output:
  

• Please complete this pull request review by [Fill in date].
  

Pull Request Checklist

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• Complete the PR definition above.
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  Select: Milestone as the version that will include these changes
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• Close the linked issue and delete your feature or bugfix branch from GitHub.

[JohnHalleyGotway]

I approve of these changes.

I reviewed the small set of code changes, but also tested the compiled code. I confirmed that...

1. Specifying the '@' symbol forces the interpretation of the value.
2. Omitting the '@' symbol forces the interpretation of the dimension index.
3. The use of '@' remains optional when specifying the value as a timestring in YYYYMMDD_HH[MMSS] format, where the MMSS part is optional.