CODEWITHSUNDEEP
functionstructtypesjulia
ahm5
ahm5

Reputation: 683

how to make a function that create a variable?

I want to make a function that create a new variable, my goal is:

   struct Test

  setArg(varName,Float64,10.1,1.2)

   end

That should return a struct Test with one argument varName from the Type Float64 with max 10.1 and min 1.2. My problem is to know how to make the that function return a variable.

Or I'm thinking in another approach like this:

struct Test

      varName::setArg(Float64,10.1,1.2)

  end

here the function should just define a Type and max and min for the argument and that is okay, but I will prefer the first one if it is possible to do it in Julia.

So the question is how should my function/Type setArg look like?

Upvotes: 0

Views: 74

Answers (1)

longemen3000
longemen3000

Reputation: 1313

You could create an incomplete mutable struct:

struct MyTest{T} #to allow different types while maintaining performance
  min::T
  max::T
  val::T
  valueset::Bool #to check if the struct is initialized
  sym::Symbol #to access
end

to allow the user to access the value with the identifier provided, we overload Base.getproperty for the MyTest struct:

function Base.getproperty(val::MyStruct, sym::Symbol) 
#identifier matches and the value was set
  if val.sym==sym &  val.valueset
    return val.val
  else
    throw(error("oops") 
  end
end

finally, we make the struct with setArg:

function setArg(sym, type, min, max) 
  min = convert(type, min) 
  max = convert(type, max) 
  dummyval = zero(type) #
  return MyTest(min, max, dummyval, false, sym) 
end

finally, we make a function that sets the value, by calling the struct:

function (val::MyTest)(value) #a functor
  if val.min <= value <= val.max
    val.val = value
    val.valueset = true
  else
    throw(error("out of bounds")) 
  end
  return val
end

I imagine that the usecase is something like this :

constructor = setArg(:myname, Float64, 0.2, 0.5)
val1 = constructor(0.4)
val2 = constructor(0.5) 
val3 = constructor(0.6) #error
val2.myname == 0.5

Upvotes: 1

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