[IronPython] Writing cross-language libraries that appear native

[Jimmy Schementi]

For #3, you can avoid using an object argument and casting by typing the argument as the the non-generic IList and IDictionary.

I think you're correct with #2 as F# doesn't support Nullable<T> syntactically, but it doesn't mean F# can't consume code using Nullable.

~Jimmy


On Apr 4, 2011, at 11:24 AM, Doug Blank <doug.blank at gmail.com> wrote:

> I'm working on writing C# libraries which can be imported by a variety
> of .NET languages, DLR and otherwise, which appear native to the
> language importing them.
> 
> For example, writing a C# function that can be used naturally in
> IronPython as if it were written in Python, IronRuby as if it were
> written in Ruby, and F# as if it were written in F#, etc.
> 
> I've encountered some gotchas that I thought I'd share, and looking
> for any other points of advice in writing cross-language libraries.
> 
> 1. IronRuby strings aren't really strings, so you need to pass them in
> as an object, and call .ToString().
> 
>    public static string expects_string(object val) {
>        return val.ToString();
>    }
> 
> 2. F# 2.0 doesn't seem to automatically convert a type to the
> associated nullable type, so avoid nullable types as parameters.
> 
>    // AVOID:
>    public static double? expects_nullable(double? var1=null) {
>        return var1;
>    }
> 
>    // BETTER:
>    public static double? expects_nullable() {
>        return null;
>    }
>    public static double expects_nullable(double var1) {
>        return var1;
>    }
> 
> 3. IronPython and IronRuby lists and dictionaries implement IList and
> IDictionary, so no problem with those.
> 
>    public static IDictionary<object,object> make_dict(object val) {
>        if (val as IDictionary<object,object> != null) {
>            return ((IDictionary<object,object>)val);
>        } else
>            throw new System.ArgumentException("object is not a dictionary");
>    }
> 
>    public static IList<object> make_list(object val) {
>        if (val as IList<object> != null) {
>            return ((IList<object>)val);
>        } else
>            throw new System.ArgumentException("object is not a list");
>    }
> 
> Any other suggestions?
> 
> -Doug
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