Step by Step solution about How to resolve the algorithm First-class functions/Use numbers analogously step by step in the Haskell programming language

This Haskell code defines a function that multiplies two numbers and a third number. It then uses this function to print a table of values, where each row shows the product of two numbers and 0.5.

Here is a breakdown of the code:

• The multiplier function takes three arguments: two numbers a and b, and a function m that takes a single argument. It returns a new function that multiplies a and b by m.

• The main function defines three lists: numbers, inverses, and pairs.

  • The numbers list contains the numbers 2.0, 4.0, and 6.0.
  • The inverses list contains the numbers 0.5, 0.25, and 1.0.
  • The pairs list contains the pairs of numbers from numbers and inverses.

• The print_pair function takes a pair of numbers as an argument and prints a formatted string to the console. The string shows the product of the two numbers and 0.5.

• The mapM_ function applies the print_pair function to each pair of numbers in the pairs list.

• The output of the program is a table of values, where each row shows the product of two numbers and 0.5. For example, the first row shows the product of 2.0 and 0.5, which is 1.0.

module Main
  where

import Text.Printf

-- Pseudo code happens to be valid Haskell
x  = 2.0
xi = 0.5
y  = 4.0
yi = 0.25
z  = x + y
zi = 1.0 / ( x + y )

-- Multiplier function
multiplier :: Double -> Double -> Double -> Double
multiplier a b = \m -> a * b * m

main :: IO ()
main = do
  let
    numbers = [x, y, z]
    inverses = [xi, yi, zi]
    pairs = zip numbers inverses
    print_pair (number, inverse) =
      let new_function = multiplier number inverse
      in printf "%f * %f * 0.5 = %f\n" number inverse (new_function 0.5)
  mapM_ print_pair pairs