Question

Ruby, which is normally very forgiving, is giving me an error on a while loop; I can’t see why.

def foo(vals)
  n = vals.length
  key = n-1
  newkey = n-1

  while ((key > 0) && (vals[key] <= vals[key-1])) key--

  key
end

The error:

prog.rb:37: syntax error, unexpected tIDENTIFIER, expecting keyword_do_cond or ';' or '\n'
    while ((key > 0) && (vals[key] <= vals[key-1])) key--
                                                       ^

Any ideas?

Answer 1

Ruby has no pre/post increment/decrement operator. We use x -= 1
and paste it before while if you want one liner.

def foo(vals)
  n = vals.length
  key = n-1
  newkey = n-1

  key -= 1 while ((key > 0) && (vals[key] <= vals[key-1]))
  key
end