Refuse the arc- spellings of the inverse hyperbolic functions

[Rafael-SOWNet]

"arcsinh(x)".ToEntity()     // master: arcsinh * x
"arctanh(x)".ToEntity()     // master: arctanh * x

A product of an undeclared variable and x, with nothing said about it. Same for arccosh, arccotanh, arcsech and arccosech.

Rewritten after review

The first version of this took those spellings as synonyms. @Happypig375 pointed out that is wrong — the inverse hyperbolic functions are area functions, not arc functions — and suggested erroring instead. That is right, and it is what this now does. arcsinh is not another name for arsinh; it is not a name for anything.

UnrecognizedFunctionParseException: there is no function arcsinh: the inverse hyperbolic
functions are area functions, not arc functions, so the inverse hyperbolic sine is
arsinh, asinh or arsh

Each of the six names its own correct spellings.

Nothing else changes

• The twenty-one spellings the grammar already accepted still parse: asinh, arsinh, arsh, acosh, arcosh, arch, atanh, artanh, arth, acoth, arcoth, acotanh, arcotanh, arcth, asech, arsech, arsch, acosech, arcosech, arcsch, acsch.
• arcsin, arccos, arctan, arccotan, arcsec and arccosec are correct names and are untouched.
• A name that merely begins the same way is still the product it was: arcs(x), arcsinhh(x), arc * x.

How

By changing AngouriMath.g and regenerating, following Docs/Contributing/ImproveParser.md — the repository's own antlr-4.13.1-complete.jar, then AntlrPostProcessorReplacePublicWithInternal. The churn in the generated files is ANTLR renumbering its tokens; the only hand-written change is six alternatives in the .g, plus one new exception type.

UnrecognizedFunctionParseException is new, next to UnrecognizedDomainException. If you would rather not add a type I can throw an existing one instead — say which.

Verification

23 tests: the six refusals each naming the right spelling, and seventeen expressions that must parse exactly as before. Four spellings that already parsed but were never exercised (acotanh, arcotanh, acosech, arcosech) are added to TestHyperbolic while passing.

4036 unit tests and 127 F# tests on both target frameworks, none failing.

[Happypig375]

It doesn't seem correct to call inverse hyberbolic functions "arc" when they actually mean "area". Maybe these should be errors instead?

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Codecov Report

❌ Patch coverage is 99.28775% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.88%. Comparing base (90c00a8) to head (593aaae).
⚠️ Report is 57 commits behind head on master.

Files with missing lines	Patch %	Lines
...ources/AngouriMath/Core/Antlr/AngouriMathParser.cs	98.57%	3 Missing and 2 partials ⚠️
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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #687      +/-   ##
==========================================
- Coverage   80.99%   80.88%   -0.11%     
==========================================
  Files         155      156       +1     
  Lines       13687    13012     -675     
  Branches     1957     2122     +165     
==========================================
- Hits        11086    10525     -561     
+ Misses       1990     1878     -112     
+ Partials      611      609       -2     

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[Rafael-SOWNet]

You're right, and thank you — I had it backwards. Rewritten to refuse them rather than accept them, with a message that says why and names the spellings that do work:

there is no function arcsinh: the inverse hyperbolic functions are area functions,
not arc functions, so the inverse hyperbolic sine is arsinh, asinh or arsh

The twenty-one spellings that already parsed are untouched, arcsin and its five relatives are correct names and untouched, and something that merely begins the same way — arcs(x), arcsinhh(x) — is still the product it was.

One thing worth your call: this adds UnrecognizedFunctionParseException next to UnrecognizedDomainException, since none of the existing parse exceptions fit "that name is not a function". If you would rather not grow the exception surface, say so and I will throw an existing one.

[Rafael-SOWNet]

Noted on the issue references, thanks — full URLs in comments from here.

I have opened #689 for the seven that were already merged, and fixed the two remaining ones in my open branches. The six that predate my work I have left alone; happy to convert those too if you want them.