Language

language.swift

class Language {
	private let separator = ", "
	private var productions = [String: [String]]()
	
	init(setUpProductionRules: Bool) {
		if setUpProductionRules {
			self.setUpProductionRules()		
		}
	}
	
	func recognize(arr1 arr1: [ParseTreeNode], arr2: [ParseTreeNode]) -> [ParseTreeNode]? {
		var nodes = [ParseTreeNode]()
		for node1 in arr1 {
			for node2 in arr2 {
				let key = [node1.nonTerminal, node2.nonTerminal].joinWithSeparator(separator)
				if let nonTerminals = productions[key] {
					for nonTerminal in nonTerminals {
						let node = ParseTreeNode(nonTerminal: nonTerminal, leftNode: node1, rightNode: node2)
						nodes.append(node)
					}
				}
			}
		}
		return (nodes.count > 0) ? nodes : nil
	}
	
	private func setUpProductionRules() {				
		addGrammar(leftHandSide: "VP", rightHandSide: ["Verb", "NP"])
		addGrammar(leftHandSide: "NP", rightHandSide: ["Det", "Noun"])
		addLexicon(leftHandSide: "Verb", rightHandSide: ["book"])
		addLexicon(leftHandSide: "Det", rightHandSide: ["that"])
		addLexicon(leftHandSide: "Noun", rightHandSide: ["flight"])				
	}
	
	func printGrammarAndLexicon() {		
		var dict = [String: [String]]()
		var keys = productions.keys
		for key in keys {
			let value = productions[key]!
			for nonTerminal in value {
				if dict[nonTerminal] == nil {
					dict[nonTerminal] = [key]
				} else {
					dict[nonTerminal]?.append(key)
				}
			}
		}
		
		keys = dict.keys
		for key in keys {
			let array = dict[key]! 
			for str in array {	
				print("\(key) -> \(str)")
			}		
		}
	}
	
	func addGrammar(leftHandSide leftHandSide: String, rightHandSide: [String]) {
		let key = rightHandSide.joinWithSeparator(separator)
		if productions[key] != nil {
			productions[key]?.append(leftHandSide)
		} else {
			productions[key] = [leftHandSide]
		}
	}
	
	func addLexicon(leftHandSide leftHandSide: String, rightHandSide: [String]) {
		for word in rightHandSide {
			if productions[word] != nil {
				productions[word]?.append(leftHandSide)
			} else {
				productions[word] = [leftHandSide]
			}
		}
	}
		
	func recognize(rightHandSide: [String]) -> [String]? {
		let key = rightHandSide.joinWithSeparator(separator)
		return productions[key]
	}
	
}