hi there is a non stable result in power operator. this is the example. when I call the power with the variable the power not works. but when calling directly it julia> a = -1.9345e6 -1.9345e6 julia> a^1.5 ERROR: DomainError with -1.9345e6: Exponentiation yielding a complex result requires a c…

The - operator has lower precedence than the ^ operator, so the expression -1.9345e6^1.5 means -(1.9345e6^1.5) rather than (-1.9345e6)^1.5. If you try the a = -1.9345e6; a^1.5 version in Matlab you’ll get the same imaginary value as complex(a)^1.5 gives in Julia. Also, please quote code in posts: …

While preparing an introductory talk about Julia on my University, I am looking and Chris Rackauckas’s notes why Julia. I am puzzled with his example with powers, as 5^5 should return an Int (and it does), whereas 5^-5 should fail. Nevertheless 5^-5 executes correctly in repl, but when I define func…

Literals are treated differently: julia> Base.Meta.@lower 5^-5 :($(Expr(:thunk, CodeInfo( 1 ─ %1 = (Core.apply_type)(Base.Val, -5) │ %2 = (%1)() │ %3 = (Base.literal_pow)(^, 5, %2) └── return %3 )))) which is equivalent to julia> Base.literal_pow(^, 5, Val(-5)) 0.0003200000000000001 jul…

[image] Tomas_Pevny: Nevertheless 5^-5 executes correctly in repl Because julia> Meta.lower(Main, :(5^-5)) :($(Expr(:thunk, CodeInfo( @ none within `top-level scope' 1 ─ %1 = Core.apply_type(Base.Val, -5) │ %2 = (%1)() │ %3 = Base.literal_pow(^, 5, %2) └── return %3 )))) note t…

I have figure that it is hitting literal_pow, but I was quite confused that @which has not pointed me to the correct method that was used.

Thanks @mauro3 and @Tamas_Papp . I do not want to achieve anything special, I am just interested in internals, how does it work. Your explanation is great, yet it adds another thing I do not understand well.

[image] mauro3: I don’t know what the reason behind this design is. Presumably to avoid having to type literal floats. Precisely, see #3024 (from the dawn of time). Personally, I would prefer that users type inv(a)^n if that’s what they want, but that adds yet another item to the list of une…

I confess that the last time I have read the manual was for Julia v0.3. I think I have a homework.

That remark was not targeted at you (but of course, re-reading the manual from time to time is great, a lot of effort goes into it and it and it is really useful), it was more about the reasons that I assume lead to the introduction of this feature. Namely, the pivotal role of type stability in Jul…

I think your remark was very sound. Thanks a lot for opening me eyes.

Weird result in power operator

New to Julia

nilshg June 6, 2020, 1:19pm 14

Integer overflow is a different issue which comes up regularly. The most recent discussion about it is here, including reasons for this behaviour, ways around it and some suggestions to make it easier on newcomers.

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Weird result in power operator

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