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POPipe forwards in C#
 

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    <p>Continuing <a href="https://stackoverflow.com/questions/308481/writing-the-f-recursive-folder-visitor-in-c-seq-vs-ienumerable">my investigation</a> of expressing F# ideas in C#, I wanted a pipe forward operator. For anything wrapped in a IEnumerable, we already have it, as you can .NextFunc() to your heart's content. But for example if you have any fold-like reduction at the end, you can't feed the result of that into a function.</p> <p>Here are two extension methods, I wondered if anyone else had tried this, and if it's a good idea or not (EDIT: now with <a href="http://#337846" rel="nofollow noreferrer">Earwicker's Maybe</a> included):</p> <pre><code>public static void Pipe&lt;T&gt;(this T val, Action&lt;T&gt; action) where T : class { if (val!=null) action(val); } public static R Pipe&lt;T, R&gt;(this T val, Func&lt;T, R&gt; func) where T : class where R : class { return val!=null?func(val):null; } </code></pre> <p>You can then write something like: </p> <pre><code>Func&lt;string, string[]&gt; readlines = (f) =&gt; File.ReadAllLines(f); Action&lt;string, string&gt; writefile = (f, s) =&gt; File.WriteAllText(f, s); Action&lt;string, string&gt; RemoveLinesContaining = (file, text) =&gt; { file.Pipe(readlines) .Filter(s =&gt; !s.Contains(text)) .Fold((val, sb) =&gt; sb.AppendLine(val), new StringBuilder()) .Pipe((o) =&gt; o.ToString()) .Pipe((s) =&gt; writefile(file, s)); }; </code></pre> <p>(I know, Filter == Where in C#, and Fold==Aggregate, but I wanted to roll my own, and I could have done WriteAllLines, but that's not the point)</p> <p>EDIT: corrections as per Earwicker's comment (if I've understood correctly).</p>
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    1. COI think this is called composing, not piping.
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    2. CONo, but they are related, look here: http://blogs.msdn.com/chrsmith/archive/2008/06/14/function-composition.aspx
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    3. COCouple of bugs: you need a constraint 'where T : class' or you can't compare with null. Also you've only put the check for null in the Func version. In an ideal world you would only need to write the Func version - see 'void' in http://stackoverflow.com/questions/27731/whats-wrong-with-c#303071
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