<div dir="ltr"><div><div><div><div><div><div><div><div><div><div><div>Actually, I remember that that chapter being difficult too, so much so that I don't think I finished it. It might be worth coming back to that chapter later, after you have more practical experience.<br>
<br></div>In the mean time though, if I could tell you only one fact about how to use Applicative, it would be this.<br><br>Say you have some pure function:<br><br></div>f :: Int -> Int -> Int -> Int<br><br></div>
And some values that may or may not be in the context of some Applicative functor (let's say Maybe)<br><br></div>x :: Maybe Int<br></div>y :: Int<br></div>z :: Maybe Int<br><br></div>Then you can call f like this:<br>
<br></div>(f <$> x <*> pure y <*> z ) :: Maybe Int<br><br></div>So if you were in the middle of some do notation you could<br><br></div><div>do<br></div> myF <- f <$> x <*> pure y <*> z<br>
...<br><br></div>rather than the more painful<br><div><div><div><div><div><div><div><div><div><div><div><br><div>do<br></div><div> x' <- x<br></div><div> z' <- z<br></div> let myF = f x' y z'<br>
...<br><br><br><br><br><br> </div></div></div></div></div></div></div></div></div></div></div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Wed, Aug 27, 2014 at 10:22 AM, Peter Hall <span dir="ltr"><<a href="mailto:peterjoel@gmail.com" target="_blank">peterjoel@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div class="">><span style="color:rgb(31,73,125);font-family:Calibri,sans-serif;font-size:15px"> I learned a new word today, “Sisyphean.”</span><div>
<font color="#1f497d" face="Calibri, sans-serif"><span style="font-size:15px"><br>
</span></font></div></div><div><font color="#1f497d" face="Calibri, sans-serif"><span style="font-size:15px">Me too! :)</span></font></div><span class="HOEnZb"><font color="#888888"><div><font color="#1f497d" face="Calibri, sans-serif"><span style="font-size:15px"><br>
</span></font></div>
</font></span><div><span class="HOEnZb"><font color="#888888"><font color="#1f497d" face="Calibri, sans-serif"><span style="font-size:15px">Peter<br></span></font></font></span><div class="gmail_extra"><br><br><div class="gmail_quote">
<div><div class="h5">On 27 August 2014 04:21, Jeff C. Britton <span dir="ltr"><<a href="mailto:jcb@iteris.com" target="_blank">jcb@iteris.com</a>></span> wrote:<br>
</div></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div><div class="h5">
<div link="#0563C1" vlink="#954F72" lang="EN-US">
<div>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">I had originally encountered problems at this point myself. I lost motivation because I had just had this feeling that programming with applicatives was just
not going to be fun, and it was beginning to seem like Haskell programming might involve a lot of this. I put the book down for about 1 year. Somewhere I came across an article on Monads that changed my mind. I started over and am now almost done with Chapter
13. This time around things are looking a lot cooler. I think chapters 11,12, and 13 may lack the motivational information to keep one going. I can say that the author Miran Lipovaca really does a great job of explaining this material. I don’t think you
are going to find a better source. Absolutely every step of the way is laid out in painstaking detail. Plus there are constant reminders of material that was just covered that is relevant to the immediate situation. All I can say is go slow and make sure
you understand every detail before proceeding. Keep at it regularly so as not to forget important terms. Go back and reread if necessary. Have the confidence that it will be worthwhile. The Monad chapters are little bit more interesting, but you will need
to understand the applicatives first. I learned a new word today, “Sisyphean.”<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"><u></u> <u></u></span></p>
<p class="MsoNormal"><b><span style="font-size:11pt;font-family:Calibri,sans-serif">From:</span></b><span style="font-size:11pt;font-family:Calibri,sans-serif"> Beginners [mailto:<a href="mailto:beginners-bounces@haskell.org" target="_blank">beginners-bounces@haskell.org</a>]
<b>On Behalf Of </b>Frank<br>
<b>Sent:</b> Tuesday, August 26, 2014 7:33 PM<br>
<b>To:</b> The Haskell-Beginners Mailing List - Discussion of primarily beginner-level topics related to Haskell<br>
<b>Subject:</b> [Haskell-beginners] LYAHFGG, chapter 11 question<u></u><u></u></span></p><div><div>
<p class="MsoNormal"><u></u> <u></u></p>
<div>
<p class="MsoNormal">About "Learn You a Haskell ...", is it My imagination or is chapter 11 absurdly long and/or thick? I can (and have) read a 100+ page U.S. Supreme Court ruling, readily understand it, and be able to explain it in plain English, with next
to zero trouble. I spend every work day reading, parsing, interpreting, and using, the ISO C++ standard. I
<i>taught</i> My undergraduate Physics IV class while simultaneously taking it. Yet, chapter 11 feels as if it goes on and on to the point I easily forget what I read just a few lines before, rendering comprehension of the same an almost Sisyphean task. Is
it just Me? Am I just tired? Is there an alternative resource for understanding the concepts that particular chapter presents?<u></u><u></u></p>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
<div>
<p class="MsoNormal">Sincerely,<u></u><u></u></p>
</div>
<div>
<p class="MsoNormal">Frank D. Martinez<br clear="all">
<u></u><u></u></p>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
<p class="MsoNormal">-- <br>
P.S.: I prefer to be reached on BitMessage at BM-2D8txNiU7b84d2tgqvJQdgBog6A69oDAx6
<u></u><u></u></p>
</div>
</div>
</div></div></div>
</div>
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