Answer for Ninputer: merge spaces

mergeSpaces.moe

def rest(s) = s.slice 1

def mergeSpaces(s) = phase_normal s
where phase_normal(s) = piecewise
          when(not s)       s
          when(s[0] == ' ') s[0] + phase_space rest s
          otherwise         s[0] + phase_normal rest s
      phase_space(s) = piecewise
          when(not s)       s
          when(s[0] == ' ') phase_space rest s
          otherwise         s[0] + phase_normal rest s

trace mergeSpaces 'abc   def'
trace mergeSpaces 'abc def'
trace mergeSpaces 'a    bcd   ef'
trace ('[' + mergeSpaces '             ' + ']')