99 questions/Solutions/95
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(**) English number words
On financial documents, like cheques, numbers must sometimes be written in full words. Example: 175 must be written as one-seven-five. Write a predicate full-words/1 to print (non-negative) integer numbers in full words.
import Data.Char
import Data.List
fullWords :: Integer -> String
fullWords n = concat $ intersperse "-" [digits!!digitToInt d | d <- show n]
where digits = ["zero", "one", "two", "three", "four",
"five", "six", "seven", "eight", "nine"]
This solution does a simple table lookup after converting the positive integer into a string. Thus dividing into digits is much simplified.