Question

Is there a way to use Haskell’s “map” or something similar with multiple arguments?

i.e. to find the distance between a given point (defined as a tuple) and a list of other points:

map distance (-3,-3) buildings

Clearly, that doesn’t work, because it tries to map “distance” to (-3,-3), where distance expects two tuples:

let distance pointA pointB = sqrt ( (frst pointB - frst pointA) * (frst pointB - frst pointA) + (scnd pointB - scnd pointA) * (scnd pointB - scnd pointA) )

distance takes two points as arguments: one is (-3,-3) in this example, and one is selected from the list “buildings”.

(-3,-3) is just an example. This will have to be a variable; it can’t be hardcoded into the function.

Maybe this will make a little more sense:

buildings = [(3,-2),(2,1),(5,3),(4,3),(4,-1)]

firstDiff pointA pointB = subtract ( fst pointA ) ( fst pointB )

secondDiff pointA pointB = subtract ( snd pointA ) ( snd pointB )

distance pointA pointB = sqrt ( (firstDiff pointA pointB) * (firstDiff pointA pointB) +     (secondDiff pointA pointB) * (secondDiff pointA pointB))

--- What I need to happen here is a list "score" to be created by taking all distances from a point in a list lPoints to a point in list buildings.

Answer 1

you want:

map (distance (-3, -3)) buildings

which is

map f buildings 
  where f = distance (-3, -3)