For loop on a structure's field names

[piever]

@francesco123212

I am trying to implement the dempster’s model to perform some calculations on a human body inertial properties. In order to do that the body is divided in 14 segments, each of which has its own length, mass, centre of mass,…

The structure a mentioned above would be a collector of the segments, so:

struct a
   head&neck::b
   right fore arm::b
   right thigh::b
   .....
end

while the structure b a collector of the properties, so

mutable struct b
   segment length::float64
   segment mass::float64
   ....
end

The structure is mutable since some values of the field are calculated in a function, it works, but I dont know if it is the best way to do it.

If each “body” is some overall info about the body (height, weight, subject identity, etc…) and a list of segments, you could probably organize it as

struct Segment
    length::Float64
    mass::Float64
end
struct Body
    height::Float64
    segments::Vector{Segment}
end

and now body.segments[i] gives you the i-th segment. Note that you probably don’t need to make Segment mutable: you can just set the i-th element of the vector to a new Segment struct, without mutating the old one (it tends to be more efficient).

If body.segments[i] is a bit “unreadable” and you’d prefer to refer to the i-th segment by name (say arm or thigh) you can use (as suggested above) a data structure that is like an array, but also keeps a label, check out for example GitHub - SciML/LabelledArrays.jl: Arrays which also have a label for each element for easy scientific machine learning (SciML) (there are many alternatives, I personally haven’t really used any so can’t offer much advice here).