FiniteAutomaton from regex can't use "."

[aengelberg]

FiniteAutomaton(".")

hangs indefinitely. Probably because . means any character, and a FiniteAutomaton's alphabet is finite. Though I'd at least assume something like this would be returned:

#<FiniteAutomaton initial state: 0
state 0 [reject]:
  \u0000-\u9999 -> 1
state 1 [accept]:
>

[cprudhom]

Yes, that's a known problem. The . expresses that all letters from the alphabet are acceptable; in our case, all values from Character.MIN_VALUE to Character.MAX_VALUE. Then, the automaton is populated and all valid transitions from all known states are built; in our case, there are 65536 states and all possible transitions are valid, that is, 4294967296 iterations to add (or not) a digit to the alphabet... To avoid (temporarily) this, we added the following constructor:

  /**
  * ..
  * @param min    an overall minimum value for transitions
  * @param max    an overall maximum value for transitions
  */
public FiniteAutomaton(String regexp, int min, int max) {...}

A realistic patch would be to reimplement the REGULAR constraint on the basis of a more accurate library (we already have one in the pipes, but it is based on Java8 only).