public string ConvertAst(Node headNode)
{
var builder = new StringBuilder();
ConvertNode(headNode, builder);
return builder.ToString();
}
private void AddNodeText(Node node, StringBuilder builder, string prefix)
{
var prefixChar = 'a';
var colour = node.IsTerminal ? " fillcolor=\"gold\" style=\"filled\"" : "";
builder.AppendLine($" {prefix} [label=\"{node.Contents}\"{colour}]");
foreach (var child in node.Children)//.Where(child => !child.Contents.Contains("Null")))
{
builder.AppendLine($" {prefix} -> {prefix}{prefixChar}");
AddNodeText(child, builder, prefix + prefixChar);
prefixChar ++;
}
}
public string GenerateGraphString(Node headNode)
{
var builder = new StringBuilder("digraph G {");
builder.AppendLine(" a ;");
AddNodeText(
node: headNode,
builder: builder,
prefix: "a");
builder.AppendLine("}");
return builder.ToString();
}
public Node AddChild(Node child)
{
_children.Add(child);
return this;
}
/// <summary>
/// Adds the following grammar rules to the RDP parser passed into the function:
///
/// base -> stmt
/// stmt -> IF expr THEN stmt ELSE stmt
/// | WHILE expr DO stmt
/// | INPUT ID
/// | ID ASSIGN expr
/// | WRITE expr
/// | BEGIN stmtlist END
/// stmtlist -> stmt SEMICOLON stmtlist'
/// stmtlist' -> stmt SEMICOLON stmtlist'
/// | .
/// expr -> term expr'
/// expr' -> addop term expr'
/// | .
/// term -> factor term'
/// term' -> mulop factor term'
/// | .
/// factor -> LPAR expr RPAR
/// | ID
/// | NUM
/// | SUB NUM
/// addop -> ADD | SUB
/// mulop -> MUL | DIV
/// </summary>
/// <param name="parser">Parser that should accept the rules</param>
public static void AddRdpRules(RecursiveDescentParser parser)
{
// base -> stmt
parser.AddRule(
name: "base",
decider: rdp => true,
evaluator: rdp => rdp.InvokeRule("stmt"));
// stmt -> IF expr THEN stmt ELSE stmt
parser.AddRule( // if
name: "stmt",
decider: rdp => rdp.TryMatch(TokenType.If),
evaluator: rdp =>
{
var node = new Node {Contents = "IF Statement", Type = NodeType.If};
node.AddChild(rdp.TryConsumeToken(TokenType.If));
node.AddChild(rdp.InvokeRule("expr"));
node.AddChild(rdp.TryConsumeToken(TokenType.Then));
node.AddChild(rdp.InvokeRule("stmt"));
node.AddChild(rdp.TryConsumeToken(TokenType.Else));
node.AddChild(rdp.InvokeRule("stmt"));
return node;
});
// stmt -> WHILE expr DO stmt
parser.AddRule( // while
name: "stmt",
decider: rdp => rdp.TryMatch(TokenType.While),
evaluator: rdp =>
{
var node = new Node {Contents = "WHILE Statement", Type = NodeType.While};
node.AddChild(rdp.TryConsumeToken(TokenType.While));
node.AddChild(rdp.InvokeRule("expr"));
node.AddChild(rdp.TryConsumeToken(TokenType.Do));
node.AddChild(rdp.InvokeRule("stmt"));
return node;
});
// stmt -> INPUT ID
parser.AddRule( // input
name: "stmt",
decider: rpd => rpd.TryMatch(TokenType.Input),
evaluator: rdp =>
{
var node = new Node {Contents = "INPUT Statement", Type = NodeType.Input};
node.AddChild(rdp.TryConsumeToken(TokenType.Input));
node.AddChild(rdp.TryConsumeToken(TokenType.Id));
return node;
});
// stmt -> ID ASS expr
parser.AddRule( // assign
name: "stmt",
decider: rdp => rdp.TryMatch(TokenType.Id),
evaluator: rdp =>
{
var node = new Node {Contents = "Assign Statement", Type = NodeType.Assign};
node.AddChild(rdp.TryConsumeToken(TokenType.Id));
node.AddChild(rdp.TryConsumeToken(TokenType.Assign));
node.AddChild(rdp.InvokeRule("expr"));
return node;
});
// stmt -> WRITE expr
parser.AddRule( // write
name: "stmt",
decider: rdp => rdp.TryMatch(TokenType.Write),
evaluator: rdp =>
{
var node = new Node {Contents = "WRITE Statement", Type = NodeType.Write};
node.AddChild(rdp.TryConsumeToken(TokenType.Write));
node.AddChild(rdp.InvokeRule("expr"));
return node;
});
// stmt -> BEGIN stmtlist END
parser.AddRule( // begin
name: "stmt",
decider: rdp => rdp.TryMatch(TokenType.Begin),
evaluator: rdp =>
{
var node = new Node {Contents = "BEGIN Statement", Type = NodeType.Begin};
node.AddChild(rdp.TryConsumeToken(TokenType.Begin));
node.AddChild(rdp.InvokeRule("stmtlist"));
node.AddChild(rdp.TryConsumeToken(TokenType.End));
return node;
});
// stmtlist -> stmt SEMICOLON stmtlist'
parser.AddRule(
name: "stmtlist",
decider: rdp => rdp.TryMatch("stmt"),
evaluator: rdp =>
{
var node = new Node {Contents = "Statement List", Type = NodeType.StatementList};
node.AddChild(rdp.InvokeRule("stmt"));
node.AddChild(rdp.TryConsumeToken(TokenType.Semicolon));
node.AddChild(rdp.InvokeRule("stmtlist'"));
return node;
});
// Transformed rule
// stmtlist' -> stmt SEMICOLON stmtlist'
parser.AddRule(
name: "stmtlist'",
decider: rdp => rdp.TryMatch("stmt"),
evaluator: rdp =>
{
var node = new Node {Contents = "Statement List", Type = NodeType.MoreStatements};
node.AddChild(rdp.InvokeRule("stmt"));
node.AddChild(rdp.TryConsumeToken(TokenType.Semicolon));
node.AddChild(rdp.InvokeRule("stmtlist'"));
return node;
});
// Transformed rule
// stmtlist' -> .
parser.AddRule(
name: "stmtlist'",
decider: rdp => !rdp.TryMatch("stmt"),
evaluator: rdp => new Node {Contents = "Null Statement", Type = NodeType.Null});
// expr -> term expr'
parser.AddRule(
name: "expr",
decider: rdp => rdp.TryMatch("term"),
evaluator: rdp =>
{
var node = new Node {Contents = "Expr Statement", Type = NodeType.Expression};
node.AddChild(rdp.InvokeRule("term"));
node.AddChild(rdp.InvokeRule("expr'"));
return node;
});
// Transformed rule
// expr' -> addop term expr'
parser.AddRule(
name: "expr'",
decider: rdp => rdp.TryMatch("addop"),
evaluator: rdp =>
{
var node = new Node {Contents = "Expr' Statement", Type = NodeType.MoreExpression};
node.AddChild(rdp.InvokeRule("addop"));
node.AddChild(rdp.InvokeRule("term"));
node.AddChild(rdp.InvokeRule("expr'"));
return node;
});
// Transformed rule
// expr' -> .
parser.AddRule(
name: "expr'",
decider: rdp => !rdp.TryMatch("addop"),
evaluator: rdp => new Node {Contents = "Null expr", Type = NodeType.Null});
// term -> factor term'
parser.AddRule(
name: "term",
decider: rdp => rdp.TryMatch("factor"),
evaluator: rdp =>
{
var node = new Node {Contents = "Term statement", Type = NodeType.Term};
node.AddChild(rdp.InvokeRule("factor"));
node.AddChild(rdp.InvokeRule("term'"));
return node;
});
// Transformed rule
// term' -> mulop factor term'
parser.AddRule(
name: "term'",
decider: rdp => rdp.TryMatch("mulop"),
evaluator: rdp =>
{
var node = new Node {Contents = "Term' statement", Type = NodeType.MoreTerms};
node.AddChild(rdp.InvokeRule("mulop"));
node.AddChild(rdp.InvokeRule("factor"));
node.AddChild(rdp.InvokeRule("term'"));
return node;
});
// Transformed rule
// term' -> .
parser.AddRule(
name: "term'",
decider: rdp => !rdp.TryMatch("mulop"),
evaluator: rdp => new Node {Contents = "Null term", Type = NodeType.Null});
// mulop -> MUL
parser.AddRule(
name: "mulop",
decider: rdp => rdp.TryMatch(TokenType.Mul),
evaluator: rdp => rdp.TryConsumeToken(TokenType.Mul));
// mulop -> DIV
parser.AddRule(
name: "mulop",
decider: rdp => rdp.TryMatch(TokenType.Div),
evaluator: rdp => rdp.TryConsumeToken(TokenType.Div));
// addop -> ADD
parser.AddRule(
name: "addop",
decider: rdp => rdp.TryMatch(TokenType.Add),
evaluator: rdp => rdp.TryConsumeToken(TokenType.Add));
// addop -> SUB
parser.AddRule(
name: "addop",
decider: rdp => rdp.TryMatch(TokenType.Sub),
evaluator: rdp => rdp.TryConsumeToken(TokenType.Sub));
// factor -> LPAR expr RPAR
parser.AddRule(
name: "factor",
decider: rdp => rdp.TryMatch(TokenType.LPar),
evaluator: rdp =>
{
var node = new Node {Contents = "Factor statement", Type = NodeType.Factor};
node.AddChild(rdp.TryConsumeToken(TokenType.LPar));
node.AddChild(rdp.InvokeRule("expr"));
node.AddChild(rdp.TryConsumeToken(TokenType.RPar));
return node;
});
// factor -> ID
parser.AddRule(
name: "factor",
decider: rdp => rdp.TryMatch(TokenType.Id),
evaluator: rdp =>
{
var node = new Node {Contents = "Factor statement", Type = NodeType.Factor};
node.AddChild(rdp.TryConsumeToken(TokenType.Id));
return node;
});
// factor -> NUM
parser.AddRule(
name: "factor",
decider: rdp => rdp.TryMatch(TokenType.Num),
evaluator: rdp =>
{
var node = new Node {Contents = "Factor statement", Type = NodeType.Factor};
node.AddChild(rdp.TryConsumeToken(TokenType.Num));
return node;
});
// factor -> SUB NUM
parser.AddRule(
name: "factor",
decider: rdp => rdp.TryMatch(TokenType.Sub),
evaluator: rdp =>
{
var node = new Node {Contents = "Factor statement", Type = NodeType.Factor};
node.AddChild(rdp.TryConsumeToken(TokenType.Sub));
node.AddChild(rdp.TryConsumeToken(TokenType.Num));
return node;
});
}
private void ProcessFactor(Node node, StringBuilder builder)
{
switch (node.Children.Count)
{
case 3:
ConvertNode(node.Children[1], builder);
break;
case 2:
// [-] [num]
builder.AppendLine($" cPUSH -{node.Children[1].Data}");
break;
default:
builder.AppendLine(node.Children[0].TerminalTokenType == TokenType.Id
? $" rPUSH {node.Children[0].Data}"
: $" cPUSH {node.Children[0].Data}");
break;
}
}
private void ConvertNode(Node node, StringBuilder builder)
{
switch (node.Type)
{
case NodeType.If:
ProcessIf(node, builder);
break;
case NodeType.Begin:
// of the form [BEGIN] [statement list] [END]
ConvertNode(node.Children[1], builder);
break;
case NodeType.While:
ProcessWhile(node, builder);
break;
case NodeType.Factor:
ProcessFactor(node, builder);
break;
case NodeType.Expression:
case NodeType.Term: // has the form [term] [expr']
ConvertNode(node.Children[0], builder);
ConvertNode(node.Children[1], builder);
break;
case NodeType.StatementList:
// has the form [stmt] [;] [stmtlist']
ConvertNode(node.Children[0], builder);
ConvertNode(node.Children[2], builder);
break;
case NodeType.MoreExpression:
// of the form [addop] [term] [moreexpr]
ConvertNode(node.Children[2], builder); // more expr
ConvertNode(node.Children[1], builder); // term
builder.AppendLine( // postfix the add/sub
node.Children[0].TerminalTokenType == TokenType.Add ?
" OP2 +" : " OP2 -");
break;
case NodeType.MoreTerms:
// of the form [mulop] [factor] [moreterm]
ConvertNode(node.Children[2], builder); // more expr
ConvertNode(node.Children[1], builder); // term
builder.AppendLine( // postfix the add/sub
node.Children[0].TerminalTokenType == TokenType.Mul ?
" OP2 *" : " OP2 /");
// has the form
break;
case NodeType.Terminal: // may not be needed
break;
case NodeType.Null: // nothing to add
break;
case NodeType.Input:
// of the form [INPUT] [ID]
builder.AppendLine($" READ {node.Children[1].Data}");
break;
case NodeType.Assign:
// has the form [ID] [:=] [Expr]
ConvertNode(node.Children[2], builder);
builder.AppendLine($" LOAD {node.Children[0].Data}");
break;
case NodeType.Write:
// of the form [WRITE] [expr]
ConvertNode(node.Children[1], builder);
builder.AppendLine(" PRINT");
break;
case NodeType.MoreStatements:
// of the form [stmt] [;] [morestmt]
ConvertNode(node.Children[0], builder);
ConvertNode(node.Children[2], builder);
break;
default:
throw new ArgumentOutOfRangeException();
}
}
private void ProcessWhile(Node headNode, StringBuilder builder)
{
// of the form [WHILE] [expr] [DO] [stmt]
var headLabel = GenerateLabel();
var exitLabel = GenerateLabel();
// make labels first
builder.AppendLine($"{headLabel}:");
ConvertNode(headNode.Children[1], builder); // eval expr
// decision branch
builder.AppendLine($" cJUMP {exitLabel}");
ConvertNode(headNode.Children[3], builder); // do statement
// skip back, and add follow label
builder.AppendLine($" JUMP {headLabel}");
builder.AppendLine($"{exitLabel}:");
}
private void ProcessIf(Node headNode, StringBuilder builder)
{
// of the form [IF] [expr] [THEN] [stmt] [ELSE] [stmt]
var elseLabel = GenerateLabel();
var skipLabel = GenerateLabel();
ConvertNode(headNode.Children[1], builder);
builder.AppendLine($" cJUMP {elseLabel}");
ConvertNode(headNode.Children[3], builder);
builder.AppendLine($" JUMP {skipLabel}");
builder.AppendLine($"{elseLabel}:");
ConvertNode(headNode.Children[5], builder);
builder.AppendLine($"{skipLabel}:");
}
/// <summary>
/// Generates the graphviz representation of the AST
/// </summary>
/// <param name="parentNode">root node of the AST</param>
private static void GenerateGraphvis(Node parentNode)
{
Console.WriteLine("Writing to graphviz format...");
File.WriteAllText("graphviz.dot",
new GraphVizGenerator().GenerateGraphString(parentNode));
}
/// <summary>
/// Generates the stack machine code defined in the assignment description
/// </summary>
/// <param name="parentNode">Root node of the AST</param>
private static void GenerateCompiledCode(Node parentNode)
{
Console.WriteLine("Writing compiled code...");
File.WriteAllText("StackCode.txt",
new StackMachineConverter().ConvertAst(parentNode));
}
