Feature: Render answer sets as excel workbooks (xlsx files)

[madmike200590]

In order to aid data exploration and visualization, this PR introduces a new feature, allowing answer sets to be written as xlsx files rather than just printed to stdout.

API Changes and Additions

• new package at.ac.tuwien.kr.alpha.api as top-level package for public API types (such as Alpha.java)
• Interface AnswerSetToObjectMapper<T> defining a mapping function from AnswerSet to a type parameter T
• Mapper implementation to map from AnswerSet to Workbook, i.e. xlsx workbooks. Implementation is realized using Apache POI using the approach outlined here

Commandline-Interface

• New argument -wx <path>: When set, answer sets will be written to xlsx files at the given path, e.g. the call java -jar alpha.jar -i prog.asp -wx /some/dir/progAnswerSet will result in the first answer set being written to /some/dir/progAnswerSet.1.xlsx, the second answer set to /some/dir/progAnswerSet.2.xlsx etc.

XLSX Workbook structure

• One worksheet (i.e. "tab") for each predicate with arity greater zero
• One worksheet "Flags" listing all predicates with arity zero
• In predicate-specific worksheets, each row corresponds to one atom, where columns correspond to the terms of the atom in question

[codecov]

Codecov Report

Merging #219 into master will decrease coverage by <.01%.
The diff coverage is 76.78%.

@@             Coverage Diff              @@
##             master     #219      +/-   ##
============================================
- Coverage        79%   78.99%   -0.01%     
- Complexity     2071     2091      +20     
============================================
  Files           145      147       +2     
  Lines          6582     6689     +107     
  Branches       1152     1162      +10     
============================================
+ Hits           5200     5284      +84     
- Misses          979     1001      +22     
- Partials        403      404       +1

Impacted Files	Coverage Δ	Complexity Δ
src/main/java/at/ac/tuwien/kr/alpha/api/Alpha.java	84.21% <ø> (ø)	11 <0> (?)
...java/at/ac/tuwien/kr/alpha/config/InputConfig.java	71.79% <28.57%> (-9.46%)	15 <1> (+1)
...t/ac/tuwien/kr/alpha/config/CommandLineParser.java	82.17% <42.85%> (-1.92%)	26 <0> (ø)
src/main/java/at/ac/tuwien/kr/alpha/Main.java	46.77% <47.05%> (-1.06%)	5 <2> (+1)
...a/at/ac/tuwien/kr/alpha/AnswerSetToXlsxWriter.java	92.3% <92.3%> (ø)	3 <3> (?)
...pha/api/mapper/impl/AnswerSetToWorkbookMapper.java	95.83% <95.83%> (ø)	14 <14> (?)
...in/java/at/ac/tuwien/kr/alpha/common/Interner.java	100% <0%> (+10%)	4% <0%> (+1%)	⬆️

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[AntoniusW]

The functionality provided by this PR will be of high value to many users. There are some minor comments left but overall looks very good.

[madmike200590]

@AntoniusW I made the changes we discussed on Wednesday - Sheets now have a header line, with columns labelled "Attribute x", with 1 <= x <= N and N being the arity of the predicate in question. Furthermore, when the input is unsatisfiable and xlsx output is set, a workbook with one sheet and the content "Input is unsatisfiable - No answer sets!" is written. Also added a few more tests. PR is ready for merging from my end.

[AntoniusW]

The coverage can be further improved by testing the UNSAT case.

[madmike200590]

The coverage can be further improved by testing the UNSAT case.

Added a testcase for that. The real problem with coverage is that the changes in Main are hard to test without writing lots of code..