[mLite] Convert to Binary Notation

A short diversion: the Standard ML dialect called mLite is where I go for the intellectual challenge of thinking in a functional programming way. Kudos to Nils M. Holm for developing it. mLite is one of the languages I use to solve RosettaCode tasks, in this case, Binary Digits.

This turned out to be a fairly simple task and only took me a few minutes to solve. Granted, I reused some code from the logarithm calculator of a few postings ago, but that was just for the conversion of a list of numbers to their printable form.

fun binary
   (0, []) = "0"
 | (0, x) = implode ` map (fn x = if int x then chr (x + 48) else x) x
 | (n, b) = binary (n div 2, n mod 2 :: b)
 | n = binary (n, [])
; 

The gist of that is

• pass in a number and recurse with the number and an empty list.
  
• With a number that isn't zero recurse with the number divved by 2 and the list prepended with the number modded by 2.
  
• Keep going until the number is zero. At that point, convert the answer's digits to string representation and implode them into a single string.
  
• If the number is zero and there are no digits, return "0"

Might get back to some VB6 next. Or javascript. © Copyright Bruce M. Axtens, 2015