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POProject new values from existing value
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  1. POProject new values from existing value
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    copied!<p>I'm writing my very first F# program, the aim being simply to learn F#.</p> <p>What I want to is provide a list of dates, and attributes (e.g.DayOfWeek, DayOfMonth) of those dates. I have managed to provide the list of dates and I know that the .net Framework gives me everything I need to extract all the attributes, I just can't figure out how to add the attribute as new columns in my list. Here's what I have so far:</p> <pre><code>type Span = Span of TimeSpan with static member (+) (d:DateTime, Span wrapper) = d + wrapper //this is defining the + operator static member Zero = Span(new TimeSpan(0L)) type Dates() = let a = DateTime.Parse("01/12/2013") let b =DateTime.Parse("02/12/2013") let ts = TimeSpan.FromDays(1.0) member this.Get() = [a .. Span(ts) .. b] let mydates = new Dates() mydates.Get() </code></pre> <p>When I run that code I get a list of DateTime values, with 2 records in the list. I can now do something like this:</p> <pre><code>mydates.Get() |&gt; List.map (fun x -&gt; x.DayOfWeek);; </code></pre> <p>which returns:</p> <blockquote> <p>val it : DayOfWeek list = [Sunday; Monday]</p> </blockquote> <p>or </p> <pre><code>mydates.Get() |&gt; List.map (fun x -&gt; x.DayOfYear);; </code></pre> <p>which returns:</p> <blockquote> <p>val it : int list = [335; 336]</p> </blockquote> <p>That's all great, however what I would like to do is project a list that has 2 "columns" (if columns is the right word) so that my output is (something like):</p> <blockquote> <p>val it : int list = [(Sunday,335); (Monday,336)]</p> </blockquote> <p>I hope that explains what I'm after.</p> <p>thanks</p> <p>Jamie</p>
 

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