TermUtils.isReal(IStrategoTerm, double) does not follow standard Stratego term equality

[Apanatshka]

Stratego is weird. Equality between two Real terms (double precision floating point numbers) is done with Java's built-in == operator, despite how common wisdom for comparing floats goes by comparing if their difference in under a certain threshold. TermUtils uses a fuzzy equals that uses difference under a threshold of 1e-30. I think to avoid more confusion, it should instead use the equality that Stratego uses for terms everywhere else. Thoughts?

mb-rep/org.spoofax.terms/src/org/spoofax/terms/util/TermUtils.java

Line 96 in 0168416

return isReal(term) && fuzzyEquals(((IStrategoReal)term).realValue(), value);

[Virtlink]

If the rest of Stratego uses == for floating-point equality, then that should be changed. In practice, two floating points are rarely exactly equal, so matching will almost always fail.

[Apanatshka]

Yeah, here is just one of the places where this happens:

mb-rep/org.spoofax.terms/src/org/spoofax/terms/StrategoReal.java

Line 75 in 0168416

if(realValue() != ((IStrategoReal) second).realValue())

Ok, can you change it then @Virtlink? I know it's a silly way to do comparisons this way, but there is not much use of floating points in Stratego anyway.
Perhaps we can add a strategy to the standard library of Stratego for proper comparison of reals like real-diff-within(|real) :: (real, real) -> (real, real) where you provide the epsilon value yourself. But that's separate from this issue.

[Gohla]

Changing this probably will not affect anything, as I don't think we ever use floats in Stratego, let alone compare them. But to be sure, the change should be tested by creating a new spoofax-libs.jar, copying that to strategoxt (https://github.com/metaborg/strategoxt/blob/master/strategoxt/stratego-libraries/java-backend/java/spoofax-libs.jar), and by building (bootstrapping?) strategoxt.