yes you can, it's actually better to encapsulate all "lambdas" and intermediate values inside one function, provided you never use them anywhere else. i advise using "where" as such: md n = dist (Point (fx n) (fy n)) (Point (gx n) (gy n)) where fx n = 4.0 + 0.5 * n fy n = 4.0 - 0.5 * n gx n = n * 1.0 gy n = n * (-1.0) -- then you can call "foo = md 2" it's more idiomatic to use where, i believe. however you can also choose to define the helpers before the expression defining the function, using "let ... in" like that: md n = let fx n = 4.0 + 0.5 * n fy n = 4.0 - 0.5 * n gx n = n * 1.0 gy n = n * (-1.0) in dist (Point (fx n) (fy n)) (Point (gx n) (gy n)) be careful about the alignment. both ways are (in this example) strictly equivalent, it all depends on circumstances and taste. mind you if you don't want a function to be reused, merely one single value foo = md 2, you can always just write directly: foo = dist (Point (fx 2) (fy 2)) (Point (gx 2) (gy 2)) where fx n = 4.0 + 0.5 * n fy n = 4.0 - 0.5 * n gx n = n * 1.0 gy n = n * (-1.0) 2017-06-26 11:38 GMT+02:00 PATRICK BROWNE :

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, Pat

data Point a = Point { abscissa :: a, ordinate :: a } deriving Show dist a b = sqrt (((abscissa a) - (abscissa b))^2 + ((ordinate a) - (ordinate b))^2)

-- 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

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.ie

Is 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.ie

Tá ITBÁC ag aistriú go Gráinseach Ghormáin – DIT is on the move to Grangegorman http://www.dit.ie/grangegorman

_______________________________________________ Beginners mailing list Beginners@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners