regex - regular expression: a line of string contains only float numbers and tab/spaces

Question

what the regular expression of a line of string containing ONLY float numbers separated with spaces or tabs. The float number can be negative, like -999.999

Answer 1

(?:-?(?:d+(?:.d*)|.d+)[ ]*)+

is one possibility. In more readable format:

(?:
  -?                 # Optional negative sign
  (?:
    d+(?:.d*)     # Either an integer part with optional decimal part
    |
    .d+             # Or a decimal part that starts with a period
  )
  [ ]*             # Followed by any number of tabs or spaces
)+                   # One or more times