Click here to Skip to main content
15,861,125 members
Articles / Programming Languages / Javascript

Implementing Programming Languages Using C# 4.0

Rate me:
Please Sign up or sign in to vote.
4.92/5 (115 votes)
12 Jul 2012MIT17 min read 229.2K   3.6K   249  
An introduction to creating programming language tools using C# 4.0.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Diggins.Jigsaw
{
    class ListFusion
    {
        public static IEnumerable<ResultT> Comprehension<SourceT, ResultT>(IEnumerable<SourceT> source, 
            Func<SourceT, ResultT> transform, Func<SourceT, bool> predicate)
        {
            return source.Where(predicate).Select(transform);
        }

        public static IEnumerable<ResultT> Map<SourceT, ResultT>(IEnumerable<SourceT> source,
            Func<SourceT, ResultT> transform)
        {
            return Comprehension(source, transform, x => true);
        }

        public static IEnumerable<SourceT> Filter<SourceT>(IEnumerable<SourceT> source,
            Func<SourceT, bool> predicate)
        {
            return Comprehension(source, x => x, predicate);
        }


        /*
        public static U GenFold<T, U>(T x, U init, Func<U, T, U> f, Predicate<T> halt, Func<T, T> next)
        {
            var result = init;
            while (!halt(x))
            {
                result = f(result, x);
                x = next(x);
            }
            return result; 
        }

        public static U GenFold<T, U>(T x, U init, Func<U, U, U> f, Predicate<T> halt, Predicate<T> select, Func<T, U> map, Func<T, T> next)
        {
            return GenFold(x, init, (u, t) => select(t) ? f(map(t), u) : u;  
        }
        
        public static dynamic Fold(Func<object, object, object> f, object acc, List xs)
        {
            return GenFold<List, object>(xs, acc, f, ys => ys.IsEmpty, ys => true, ys => ys, ys => ys.Tail);
        }

        public static dynamic Map(Func<object, object> f, List xs)
        {
            return GenFold(xs, List.Empty, (y, ys) => List.Cons(y, (List)ys), ys => ((List)ys).IsEmpty, y => true, f, ys => xs.Tail);
        }

        public static dynamic Filter(Predicate<object> p, List xs)
        {
            return GenFold(xs, List.Empty, (y, ys) => List.Cons(y, (List)ys), ys => ((List)ys).IsEmpty, y => p(y), ys => ys, ys => xs.Tail);
        }
        */
    }
}

By viewing downloads associated with this article you agree to the Terms of Service and the article's licence.

If a file you wish to view isn't highlighted, and is a text file (not binary), please let us know and we'll add colourisation support for it.

License

This article, along with any associated source code and files, is licensed under The MIT License


Written By
Software Developer Ara 3D
Canada Canada
I am the designer of the Plato programming language and I teach computer science at Bishop's University. I can be reached via email at cdiggins@gmail.com

Comments and Discussions