Problem Statement

The   population count   is the number of   1s   (ones)   in the binary representation of a non-negative integer. Population count   is also known as:

For example,   5   (which is   101   in binary)   has a population count of   2.

Evil numbers   are non-negative integers that have an   even   population count. Odious numbers     are  positive integers that have an    odd   population count.

Let's start with the solution:

: popcount(n)
   0 while ( n ) [ n isOdd + n bitRight(1) ->n ] ;

: test
| i count |
   30 seq map(#[ 3 swap 1- pow ]) map(#popcount) println
   
   0 ->count
   0 while( count 30 <> ) [ dup popcount isEven ifTrue: [ dup . count 1+ ->count ] 1+ ] drop printcr

   0 ->count
   0 while( count 30 <> ) [ dup popcount isOdd ifTrue: [ dup . count 1+ ->count ] 1+ ] drop ;