static void _RunCompiledLexCodeGen()
{
// create our expressions
var digits = CharFA <string> .Repeat(
CharFA <string> .Set("0123456789"),
1, -1
, "Digits");
var word = CharFA <string> .Repeat(
CharFA <string> .Set(new CharRange[] { new CharRange('A', 'Z'), new CharRange('a', 'z') }),
1, -1
, "Word");
var whitespace = CharFA <string> .Repeat(
CharFA <string> .Set(" \t\r\n\v\f"),
1, -1
, "Whitespace");
// initialize our lexer
var lexer = CharFA <string> .ToLexer(digits, word, whitespace);
// create the symbol table (include the error symbol at index/id 3)
var symbolTable = new string[] { "Digits", "Word", "Whitespace", "#ERROR" };
// create the DFA table we'll use to generate code
var dfaTable = lexer.ToDfaStateTable(symbolTable);
// create our new class
var compClass = new CodeTypeDeclaration("RegexGenerated");
compClass.TypeAttributes = System.Reflection.TypeAttributes.Class;
compClass.Attributes = MemberAttributes.Final | MemberAttributes.Static;
// add the symbol table field - in production we'll set the name
// to something more appropriate
var symtblField = new CodeMemberField(typeof(string[]), "LexSymbols");
symtblField.Attributes = MemberAttributes.Static | MemberAttributes.Public;
// generate the symbol table init code
symtblField.InitExpression = CharFA <string> .GenerateSymbolTableInitializer(symbolTable);
compClass.Members.Add(symtblField);
// Generate and add the compiled lex method code
compClass.Members.Add(CharFA <string> .GenerateLexMethod(dfaTable, 3));
// in production we'd change the name of the returned method
// above
// add the DFA table field - in production we'd change the name
var dfatblField = new CodeMemberField(typeof(CharDfaEntry[]), "LexDfaTable");
dfatblField.Attributes = MemberAttributes.Static | MemberAttributes.Public;
// generate the DFA state table init code
dfatblField.InitExpression = CharFA <string> .GenerateDfaStateTableInitializer(dfaTable);
compClass.Members.Add(dfatblField);
// create the C# provider and generate the code
// we'll usually want to put this in a namespace
// but we haven't here
var prov = CodeDomProvider.CreateProvider("cs");
prov.GenerateCodeFromType(compClass, Console.Out, new CodeGeneratorOptions());
}
static void _RunMatch()
{
var test = "foo123_ _bar";
var word = CharFA <string> .Repeat(
CharFA <string> .Set(new CharRange[] { new CharRange('A', 'Z'), new CharRange('a', 'z') }),
1, -1
, "Word");
var dfaWord = word.ToDfa();
var dfaTableWord = word.ToDfaStateTable();
CharFAMatch match;
var pc = ParseContext.Create(test);
Console.WriteLine("Matching words with an NFA:");
while (null != (match = word.Match(pc)))
{
Console.WriteLine("Found match at {0}: {1}", match.Position, match.Value);
}
Console.WriteLine();
pc = ParseContext.Create(test);
Console.WriteLine("Matching words with a DFA:");
while (null != (match = dfaWord.MatchDfa(pc)))
{
Console.WriteLine("Found match at {0}: {1}", match.Position, match.Value);
}
Console.WriteLine();
pc = ParseContext.Create(test);
Console.WriteLine("Matching words with a DFA state table:");
while (null != (match = CharFA <string> .MatchDfa(dfaTableWord, pc)))
{
Console.WriteLine("Found match at {0}: {1}", match.Position, match.Value);
}
Console.WriteLine();
pc = ParseContext.Create(test);
Console.WriteLine("Matching words with a compiled DFA:");
while (null != (match = Match(pc)))
{
Console.WriteLine("Found match at {0}: {1}", match.Position, match.Value);
}
Console.WriteLine();
}
static void _BuildArticleImages()
{
// this generates the figures used in the code project article
// at https://www.codeproject.com/Articles/5251476/How-to-Build-a-Regex-Engine-in-Csharp
var litA = CharFA <string> .Literal("ABC", "Accept");
litA.RenderToFile(@"..\..\..\literal.jpg");
var litAa = CharFA <string> .CaseInsensitive(litA, "Accept");
litAa.RenderToFile(@"..\..\..\literal_ci.jpg");
var opt = CharFA <string> .Optional(litA, "Accept");
opt.RenderToFile(@"..\..\..\optional.jpg");
var litB = CharFA <string> .Literal("DEF");
var or = CharFA <string> .Or(new CharFA <string>[] { litA, litB }, "Accept");
or.RenderToFile(@"..\..\..\or.jpg");
var set = CharFA <string> .Set("ABC", "Accept");
set.RenderToFile(@"..\..\..\set.jpg");
var loop = CharFA <string> .Repeat(litA, 1, -1, "Accept");
loop.RenderToFile(@"..\..\..\repeat.jpg");
var concat = CharFA <string> .Concat(new CharFA <string>[] { litA, litB }, "Accept");
concat.RenderToFile(@"..\..\..\concat.jpg");
var foobar = CharFA <string> .Or(new CharFA <string>[] { CharFA <string> .Literal("foo"), CharFA <string> .Literal("bar") }, "Accept");
foobar.RenderToFile(@"..\..\..\foobar_nfa.jpg");
var rfoobar = foobar.Reduce();
rfoobar.RenderToFile(@"..\..\..\foobar.jpg");
var lfoobar = CharFA <string> .Repeat(foobar, 1, -1, "Accept");
lfoobar.RenderToFile(@"..\..\..\foobar_loop_nfa.jpg");
var rlfoobar = lfoobar.Reduce();
rlfoobar.RenderToFile(@"..\..\..\foobar_loop.jpg");
var digits = CharFA <string> .Repeat(
CharFA <string> .Set("0123456789"),
1, -1
, "Digits");
var word = CharFA <string> .Repeat(
CharFA <string> .Set(new CharRange[] { new CharRange('A', 'Z'), new CharRange('a', 'z') }),
1, -1
, "Word");
var whitespace = CharFA <string> .Repeat(
CharFA <string> .Set(" \t\r\n\v\f"),
1, -1
, "Whitespace");
var lexer = CharFA <string> .ToLexer(digits, word, whitespace);
lexer.RenderToFile(@"..\..\..\lexer.jpg");
var dopt = new CharFA <string> .DotGraphOptions();
dopt.DebugSourceNfa = lexer;
var dlexer = lexer.ToDfa();
dlexer.RenderToFile(@"..\..\..\dlexer.jpg", dopt
);
dlexer.RenderToFile(@"..\..\..\dlexer2.jpg");
var dom = RegexExpression.Parse("(ABC|DEF)+");
var fa = dom.ToFA("Accept");
fa.RenderToFile(@"..\..\..\ABCorDEFloop.jpg");
}
static void _RunLexer()
{
var digits = CharFA <string> .Repeat(
CharFA <string> .Set("0123456789"),
1, -1
, "Digits");
var word = CharFA <string> .Repeat(
CharFA <string> .Set(new CharRange[] { new CharRange('A', 'Z'), new CharRange('a', 'z') }),
1, -1
, "Word");
var whitespace = CharFA <string> .Repeat(
CharFA <string> .Set(" \t\r\n\v\f"),
1, -1
, "Whitespace");
var lexer = CharFA <string> .ToLexer(digits, word, whitespace);
var lexerDfa = lexer.ToDfa();
lexerDfa.TrimDuplicates();
// we use a symbol table with the DFA state table to map ids back to strings
var symbolTable = new string[] { "Digits", "Word", "Whitespace", "#ERROR" };
// make sure to pass the symbol table if you're using one
var dfaTable = lexer.ToDfaStateTable(symbolTable);
var test = "foo123_ _bar";
Console.WriteLine("Lex using the NFA");
// create a parse context over our test string
var pc = ParseContext.Create(test);
// while not end of input
while (-1 != pc.Current)
{
// clear the capture so that we don't keep appending the token data
pc.ClearCapture();
// lex the next token
var acc = lexer.Lex(pc, "#ERROR");
// write the result
Console.WriteLine("{0}: {1}", acc, pc.GetCapture());
}
Console.WriteLine();
Console.WriteLine("Lex using the DFA");
// create a new parse context over our test string
// because our old parse context is now past the end
pc = ParseContext.Create(test);
while (-1 != pc.Current)
{
pc.ClearCapture();
// lex using the DFA. This works exactly like
// the previous Lex method except that it's
// optimized for DFA traversal.
// DO NOT use this with an NFA. It won't work
// but won't error (can't check for perf reasons)
var acc = lexerDfa.LexDfa(pc, "#ERROR");
// write the result
Console.WriteLine("{0}: {1}", acc, pc.GetCapture());
}
Console.WriteLine();
Console.WriteLine("Lex using the DFA state table");
pc = ParseContext.Create(test);
while (-1 != pc.Current)
{
pc.ClearCapture();
// Lex using our DFA table. This is a little different
// because it's a static method that takes CharDfaEntry[]
// as its first parameter. It also uses symbol ids instead
// of the actual symbol. You must map them back using the
// symbol table you created earlier.
var acc = CharFA <string> .LexDfa(dfaTable, pc, 3);
// when we write this, we map our symbol id back to the
// symbol using our symbol table
Console.WriteLine("{0}: {1}", symbolTable[acc], pc.GetCapture());
}
Console.WriteLine();
Console.WriteLine("Lex using our compiled lex method");
pc = ParseContext.Create(test);
while (-1 != pc.Current)
{
pc.ClearCapture();
// Lex using our compiledDFA. Like the table driven lex
// this also uses symbol ids instead of the actual symbol.
var acc = Lex(pc);
// when we write this, we map our symbol id back to the
// symbol using our symbol table
Console.WriteLine("{0}: {1}", symbolTable[acc], pc.GetCapture());
}
Console.WriteLine();
}
