public void TestGreibachNormalForm()
{
Assert.IsFalse(grammar1.InGreibachNormalForm());
Assert.IsFalse(grammar2.InGreibachNormalForm());
Assert.IsFalse(grammar3.InGreibachNormalForm());
Assert.IsTrue(grammar1.ToGreibachNormalForm().InGreibachNormalForm());
Assert.IsTrue(grammar2.ToGreibachNormalForm().InGreibachNormalForm());
CFG grammar3Greibach = grammar3.ToGreibachNormalForm();
Assert.IsTrue(grammar3Greibach.InGreibachNormalForm());
Assert.IsTrue(derives(grammar3Greibach, ""));
Assert.IsTrue(derives(grammar3Greibach, "()"));
Assert.IsTrue(derives(grammar3Greibach, "()()"));
Assert.IsTrue(derives(grammar3Greibach, "(())"));
Assert.IsTrue(derives(grammar3Greibach, "(()())"));
Assert.IsTrue(derives(grammar3Greibach, "()(()(()))(())"));
Assert.IsFalse(derives(grammar3Greibach, "("));
Assert.IsFalse(derives(grammar3Greibach, ")"));
Assert.IsFalse(derives(grammar3Greibach, "())"));
Assert.IsFalse(derives(grammar3Greibach, "(()()"));
Assert.IsFalse(derives(grammar3Greibach, "((())))"));
Assert.IsFalse(derives(grammar3Greibach, "(()(())"));
Assert.IsFalse(derives(grammar3Greibach, "()(()((()))(())))"));
Assert.IsTrue(CFGBuilder.Start("A")
.Derive("A").To("a")
.Derive("A").ToEpsilon()
.Build().InGreibachNormalForm());
Assert.IsFalse(CFGBuilder.Start("A")
.Derive("A").To("a", "A")
.Derive("A").ToEpsilon()
.Build().InGreibachNormalForm());
}
private static bool derives(CFG grammar, string word)
{
if (!grammar.InGreibachNormalForm())
{
throw new Exception("only grammars in Greibach normal form are supported");
}
List <string> wordList = new List <string>();
wordList.AddRange(word.Select(c => c.ToString()));
List <string> initialSententialForm = new List <string>();
initialSententialForm.Add(grammar.startVariable);
return(derives(grammar, initialSententialForm, wordList));
}