在F＃中使用属性

Question

Hopefully this is coherent, albeit longwinded.

I am trying to create a property in one .fs file that I can set from a separate .fs file and then use that value in a module in the first .fs file... For instance,

In my first file function.fs , I would like to define a property theta .

I would then like to define a function Q in function.fs such that:

function Q = Q(r) and... Q(r) is dependent on some calculations that are dependent on theta ,
ie
A1(theta), A2(theta), A3(theta)

Q returns a data set in the form of a list.

I would also like to maintain a set of theta values in my main .fs file program.fs (ie
theta = [90;120;150;180])

I would then like to generate a data sets from function.fs for each theta .

My thought was to do this by setting a value for a property theta, running the program to generate a data set, setting a new value for theta , running the program to generate a data set, repeat... I have done a fair amount of research, what is not clear to me is how I actually recall the value of the property in the code for Q(r) .

I have successfully setup a property in my function.fs file that I can set from program.fs :
In function.fs I have:

namespace models.test

type ContactAngle() =
    let mutable m_theta = 90.0
    //read only property
    member this.Empty = 
         m_theta = 90.0
     //read-write property
     //i think i'm onto something with this static...
     member this.Angle
         with get() =
             m_theta
         and set newAmt = 
             m_theta <- newAmt

//module HTModel =

And in program.fs I have:

open models.test

let me = new ContactAngle()
printfn "%A" me.Angle
me.Angle <- 120.0
printfn "%A" me.Angle

This allows me to redefine the value theta . Where I am struggling is how I now use the new property value in a function in function.fs .

I feel like I am missing something very elementary and need some help! Any insight would be greatly appreciated!

Answer 1

Since functions evaluate when they are called not when created (exactly like in, for example, C#) you can just create a normal function in your ContactAngle type like this:

member this.DoSomenthingWithTheta multiplier
    m_theta <- m_theta * multiplier

You can reuse your mutable value anywhere in your class. To clarify all that you should read 'members' section of F# language reference .

But if you want to use that value outside your type and in a place where you don't have your initiated instance. Well then You would have to take a different approach. For example create a static mutable field and expose it with static property. Or create a singleton to store your value throughout the application.

But this kind of kills the 'spirit' of functional programming :).