Language-ext: Combining Tries

[slimshader]

Hi,

I am trying to build higher abstraction based on smaller Try function components but resulting "combination" is eager in result instead of being lazy:

namespace LanguageExtTesting
{
    class Program
    {
        static Try<int> Parse(string str) => () => int.Parse(str);

        static Try<int> Sum(string lhs, string rhs)
            => from x in Parse(rhs)
               from y in Parse(lhs)
               select x + y;

        static void Main(string[] args)
        {
            var trySum = Sum("1r", "2"); // 1. throws here

            var i = trySum.Try(); // 2. instead of here
        }
    }
}

problem here is that Program currently throws in the line 1. instead of line 2. . I tried wrapping LING expression within Sum() function with additional "() =>" but then I am getting compilation error of Result not being convertible to .

[TysonMN]

This passes for me on master, so no exception is thrown anywhere.

using Xunit;

namespace LanguageExt.Tests
{
    public class Tests
    {
        static Try<int> Parse(string str) => () => int.Parse(str);

        static Try<int> Sum(string lhs, string rhs)
            => from x in Parse(rhs)
               from y in Parse(lhs)
               select x + y;

        [Fact]
        public void Test()
        {
            var trySum = Sum("1r", "2");
            var i = trySum.Try();
        }

    }
}

What version are you using?

[slimshader]

Latest NuGet version. Not that familiar with xunit, what is the assertion here?

[TysonMN]

what is the assertion here?

The implicit assertion is that no exception is thrown.

[slimshader]

Hm shouldn't then the line "var i = trySum.Try();" throw?

[TysonMN]

No, it is in the faulted state. I get the same behavior for version 3.3.28.

using LanguageExt.Common;
using Xunit;

namespace LanguageExt.Tests
{
    public class Tests
    {
        static Try<int> Parse(string str) => () => int.Parse(str);

        static Try<int> Sum(string lhs, string rhs)
            => from x in Parse(rhs)
               from y in Parse(lhs)
               select x + y;

        [Fact]
        public void Test()
        {
            var trySum = Sum("1r", "2");
            Result<int> actual = trySum.Try();
            Assert.True(actual.IsFaulted);
        }

    }
}

[louthy]

@slimshader Don't use Try<A>.Try() directly, use the other extension methods of Try<A> to work with the value. So, Try<A>.Match(...), Try<A>.IfFail(...), etc.

[slimshader]

Sorry for late reply, thanks a lot for your answers, turns out it was me being stupid and overinterpreting Visual Studio's exception notification. So to clarify: the LINQ expression I used to build Sum() function is the right way to go about combining Try<> (similarly to other monads)?

[TysonMN]

Yes. It is one is the correct ways.