Up through V11.0, Plot[Sin[x], {x, 0, 2 Pi}] === Plot[Sin[x], {x, 0, 2 Pi}] and the difference of the two sides was 0. As of V11.1, there's an Annotation on the Line, "Charting`Private`Tag$24116#1", so no two plots will be identical.

@MichaelE2 Yes. I did a bit of debugging on how ticks are created and handled and I saw this too.

is there any way to have some variables defined using Table depend on others? in particular, I would like Table[f[F, mf], {F, {0,1}}, {mF, -F, F}] to evaluate to {f[0,0], f[1,-1], f[1,0], f[1, 1], f[2,-2], f[2,-1], f[2,0], f[2,1], f[2,2]}

@JulianWolf I bet there's a better way but I use a Table within a Table and a Flatten[_,1]

tfw I transform my For loop to a Select and the run time goes down from 27 seconds to just 0.4

Why the first one is False?

MatchQ[{1}, Optional[{__Integer}, {2}]]
MatchQ[{1}, Optional[{_Integer}, {2}]]
MatchQ[{1}, {_Integer}]

@JulianWolf Why don't you try this without your typo?

@Kuba No, not really. Outside of MatchQ in a real definition it seems to work though

@halirutan ok, posted a question

@Kuba You got my upvote. Maybe @WReach can say something about this. AFAIK, besides being a god with Query he knows a good deal about patterns as well.

@halirutan I wonder if there will be a point in time when I won't be surprised by results anymore

@Kuba Patterns are infintely hard to implement and Mathematica cannot make it right in all cases. I'm sure you never reach the point where nothing surprises you. Maybe Optional is a cornercase for MatchQ. The inability to trace in depth what happens makes it even harder.

@halirutan I could reduce my wish to "be able to predict that something may fail" but I don't have high hopes for that either

@Kuba For me, Optional in this context does not really makes sense. I see it more as a function that injects an argument if it is missing. One could argue that it should use the contained pattern inside MatchQ but that would add confusion as well.

@halirutan For me it is useless/redundant but makes sense. It should represent a pattern unless I missed the point in docs.

@Kuba Yes and I see that as well. The docs suggest that it is seen as a pattern.

In beta: Wolfram University. Video tutorials, a 'scratchpad' and supporting text alongside. Impressive see example