Code Golf: Numeric Ranges

Answer 1

Python, 98 characters

def f(a):
 for x in a:
  if x-1not in a or x+1not in a:print x,"-"if x+1in a and x+2in a else",",

Python - 86 characters

This one doesn't include an extra ',' at the end

f=lambda a:''.join(`x`+",-"[(x+1in a)&x+2in a]for x in a if(x-1in a)&(x+1in a)^1)[:-1]