# Improve my lambda expressions

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## Improve my lambda expressions

 The code below provides a distance function that works for points and moving point.I am happy with the result, but I have a problem with the lambda expressions.Instead of supplying an argument to each 'mpXX', is it possible to have a single lambda argument on the entire final 'md' function? (e.g. 'md 2')Thanks in advance,Patdata Point a = Point { abscissa :: a, ordinate :: a } deriving Showdist a b = sqrt (((abscissa a) - (abscissa b))^2 + ((ordinate a) - (ordinate b))^2)-- Sttic pointsp1, p2 :: Point Floatp1 = Point 0.0 0.0p2 = Point 4.0 4.0d = dist p1 p2-- Moving pointsmp1, mp2 :: Point Floatmp1x = (\t -> 4.0 + 0.5 * t)mp1y = (\t -> 4.0 - 0.5 * t)mp1 = Point (mp1x 2) (mp1y  2)mp2x  = (\t -> 0.0 + 1.0 * t)mp2y  = (\t -> 0.0 - 1.0 * t)mp2 = Point (mp2x 2) (mp2y 2)md = dist mp1 mp2 This email originated from DIT. If you received this email in error, please delete it from your system. Please note that if you are not the named addressee, disclosing, copying, distributing or taking any action based on the contents of this email or attachments is prohibited. www.dit.ieIs ó ITBÁC a tháinig an ríomhphost seo. Má fuair tú an ríomhphost seo trí earráid, scrios de do chóras é le do thoil. Tabhair ar aird, mura tú an seolaí ainmnithe, go bhfuil dianchosc ar aon nochtadh, aon chóipeáil, aon dáileadh nó ar aon ghníomh a dhéanfar bunaithe ar an ábhar atá sa ríomhphost nó sna hiatáin seo. www.dit.ieTá ITBÁC ag aistriú go Gráinseach Ghormáin – DIT is on the move to Grangegorman_______________________________________________ Beginners mailing list [hidden email] http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
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## Re: Improve my lambda expressions

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## Re: Improve my lambda expressions

 In reply to this post by Patrick Browne On 2017-06-26 11:38, PATRICK BROWNE wrote: > The code below provides a distance function that works for points and moving > point. > I am happy with the result, but I have a problem with the lambda > expressions. [..] > -- Sttic points > p1, p2 :: Point Float > p1 = Point 0.0 0.0 > p2 = Point 4.0 4.0 > d = dist p1 p2 > > -- Moving points > mp1, mp2 :: Point Float > mp1x = (\t -> 4.0 + 0.5 * t) > mp1y = (\t -> 4.0 - 0.5 * t) > mp1 = Point (mp1x 2) (mp1y  2) > mp2x  = (\t -> 0.0 + 1.0 * t) > mp2y  = (\t -> 0.0 - 1.0 * t) > mp2 = Point (mp2x 2) (mp2y 2) > md = dist mp1 mp2 Maybe you could reduce the number of lambda expressions by extracting common logic. It seems to me that 'mp1' and 'mp2' are moved versions of the same point (2,2) except that they apply different functions to the coordinates. These functions follow a pattern (a factor is applied to the component and then an 'offset' is added). For instance, it might be worthwhile to define    movePoint :: Float -> Float -> Point -> Point    movePoint offset factor (Point x y) = Point (offset + factor * x) (offset - factor * y) ...such that you could then define md = let p = Point 2 2 in dist (movePoint 4 0.5 p) (movePoint 0 1 p) -- Frerich Raabe - [hidden email] www.froglogic.com - Multi-Platform GUI Testing _______________________________________________ Beginners mailing list [hidden email] http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
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