Back to Questions
1.3k
views3
comments
Feature Request: Heterogeneous Lists
f#

As long as we are on feature requests today, it occurred to (again) this weekend that it would be nice to be able to declare heterogeneous lists, arrays, and seq's, especially when working on things like controls.

1
2
3
4

open System.Windows.Forms
let controls = [ (new TextBox( Text="Hello, world" ) :> Control)
                 (new Button( Text="Ok" )            :> Control)
               ]

What might be nice (but there are a whole lot of other things that I would prioritize higher), would be to allow declaration of the type only once, as in:

1
2
3

let controls' = [ new TextBox( Text="Hello, world")
                  new Button( Text="Ok" )
                ] :> Control list
.

A reasonably elegant solution today is to use 'upcast' and declare the type on the variable.

1
2
3
4
5
6
7
8
9
10

 

let mylist : obj list =

    [ upcast "foo"

      upcast new System.Exception()

      upcast 32 ]
By on 4/13/2009 11:43 AM ()

Thanks Brian. I didn't know about upcast (and downcast). (I should probably read the F# language specification.)

By on 4/13/2009 1:04 PM ()

A reasonably elegant solution today is to use 'upcast' and declare the type on the variable.

Ok, that works :-)

By on 4/13/2009 11:48 AM ()

    Topic tags

    IntelliFactory Offices Copyright (c) 2011-2012 IntelliFactory. All rights reserved.
    Home | Products | Consulting | Trainings | Blogs | Jobs | Contact Us | Terms of Use | Privacy Policy | Cookie Policy     		Built with WebSharper