TIA Portal - Strange Behavior with Add Function

[drbitboy]

Yes that seems to be what Jieve writes:

I disagree: OP specifically qualified what they wrote "Of course if you know your limits, then they can be applied/tested. But for the general case, using LReal covers more bases."

I think the point is that, if the problem will not fit into 53 bits (throwing away 12 for exponent and sign), it will be a 3σ or higher case.



Noone is saying "don't think about the bits;" that is after the primary lesson of this thread, IMO. But if a certain solution works for the vast majority of cases, and memory is cheap (it was not always that way, but it generally is nowadays), why not?


I too wince as the wasted memory, but I too won't be cranky about it.

 

[Lare]

Yes that seems to be what Jieve writes:


I disagree with the "LReals as probable first choice [..]".
1st understand the problem, then choose the solution.
Not choose a solution, then go back and change it when you have understood the problem.

Maybe I am being cranky here.
When I started we had at most 16 bit integers and shift left for multiplications and shift right for divisions. And if the multiplications or divisions where not by a multiple of 2, you had to combine multiple SHL or SHR plus ADDs or SUBs to get to the desired result.
And you had to think hard about how to not saturate and also not lose resolution.
The luxury of having floating point math available does not mean you should not understand the problem as well as the solution.

Same, but I didn't need to calculate with SHL and SHRs. Have converted old programs still where that kind math was used.
My old work colleague once telled that he started his career with 8 bits (int 256) PLCs on early 80s. It have been hard to calculate to seperate bytes and combining them later on PC.