R/GrammarMaxSequenceLen.R

In gramEvol: Grammatical Evolution for R

GrammarMaxSequenceLen <- 
  function(grammar, 
           max.depth = GetGrammarDepth(grammar), 
           startSymb = GrammarStartSymbol(grammar), 
           ...) {
  # returns the maximum length of a sequence required for the grammar expression
  #    generation
  # max.depth: the maximum depth to search into the tree. It is used to avoid
  #    looping in recursive grammar
  
  if ((!IsSymbolTerminal(startSymb)) & (max.depth == 0))
    return (-1)
  
  depth = 0
  while(IsSymbolTerminal(startSymb) == FALSE) {
    sep.symbs = GetFirstNonTerminalandRest(startSymb)
    possible.choices = GetPossibleRuleChoices(sep.symbs$nonterminal, grammar)
    
    depth_list = sapply(1:possible.choices, function(choice.no) {
      chosen.rule = ChosenGrammarRule(sep.symbs$nonterminal, choice.no, grammar)
      GrammarMaxSequenceLen(grammar, max.depth - 1, startSymb = chosen.rule)
    })
    
    # break out if have no valid children
    if (max(depth_list) == -1)
      return (-1)
    
    depth = depth + 1 + max(depth_list)
    
    startSymb = sep.symbs$rest
  }
  
  return (depth)
}

GetGrammarMaxSequenceLen <- GrammarMaxSequenceLen