public BlockNode Parse()
{
var block = new BlockNode();
while (more())
{
block.AddStatement(parseStatement());
}
return(block);
}
private BlockNode ParseBlock()
{
Expect(TokenType.LBRACE);
Next();
var block = new BlockNode(Position(-1));
while (More() && !Accept(TokenType.RBRACE))
{
block.AddStatement(ParseStatement());
}
Expect(TokenType.RBRACE);
Next();
return(block);
}
private BlockNode parseBlock()
{
expect(TokenType.LBRACE);
next();
var block = new BlockNode();
while (more() && current().Type != TokenType.RBRACE)
{
block.AddStatement(parseStatement());
}
expect(TokenType.RBRACE);
next();
return(block);
}
public void BlockNodesHaveStatements()
{
var statements = new List <StatementNode>();
statements.Add(new BreakNode(SourcePosition.NIL));
statements.Add(new ContinueNode(SourcePosition.NIL));
statements.Add(new ReturnNode(SourcePosition.NIL, new NilNode(SourcePosition.NIL)));
for (var i = 0; i < statements.Count; i++)
{
subject.AddStatement(statements[i]);
}
var subjectStatements = subject.Statements.ToList();
Assert.AreEqual(subjectStatements.Count, statements.Count);
for (var i = 0; i < subjectStatements.Count; i++)
{
Assert.AreEqual(subjectStatements[i], statements[i]);
}
}
private void Statement(BlockNode pn)
{
Expression expr;
Token identifier;
switch (this.token.SymbolType)
{
case SymbolType.Variable:
// <stmt> ::= "var" <var_ident> ":" <type> [ ":=" <expr> ]
this.token = this.scanner.NextToken();
identifier = this.token;
Match(SymbolType.Identifier);
Match(SymbolType.Colon);
SymbolType type = Type();
pn.AddStatement(new DeclarationNode(identifier.Value, type, identifier));
if (this.token.SymbolType == SymbolType.Assignment)
{
this.token = this.scanner.NextToken();
expr = Expression();
pn.AddStatement(new AssignmentNode(identifier.Value, expr, identifier));
}
break;
case SymbolType.Identifier:
// <stmt> ::= <var_ident> ":=" <expr>
identifier = this.token;
this.token = this.scanner.NextToken();
Match(SymbolType.Assignment);
expr = Expression();
pn.AddStatement(new AssignmentNode(identifier.Value, expr, identifier));
break;
case SymbolType.For:
// <stmt> ::= "for" <var_ident> "in" <expr> ".." <expr> "do" <stmts> "end" "for"
this.token = this.scanner.NextToken();
identifier = this.token;
string forLoopVar = identifier.Value;
Match(SymbolType.Identifier);
Match(SymbolType.In);
expr = Expression();
AssignmentNode assignment = new AssignmentNode(identifier.Value, expr, identifier);
Match(SymbolType.Range);
expr = Expression();
BinaryExpressionNode condition = new BinaryExpressionNode(
new UnaryOperandNode(identifier.Value, SymbolType.Identifier, identifier),
"to",
new ExpressionOperandNode(expr) // BinaryExpression expects Operands
);
ForLoopNode fln = new ForLoopNode(assignment, condition, forLoopVar);
Match(SymbolType.Do);
Statements(fln);
Match(SymbolType.End);
Match(SymbolType.For);
pn.AddStatement(fln);
break;
case SymbolType.Read:
// <stmt> ::= "read" <var_ident>
this.token = this.scanner.NextToken();
identifier = this.token;
Match(SymbolType.Identifier);
pn.AddStatement(new ReadNode(identifier.Value, "", identifier));
break;
case SymbolType.Print:
// <stmt> ::= "print" <expr>
this.token = this.scanner.NextToken();
expr = Expression();
pn.AddStatement(new PrintNode(expr));
break;
case SymbolType.Assert:
// <stmt> ::= "assert" "(" <expr> ")"
this.token = this.scanner.NextToken();
Match(SymbolType.LeftParenthesis);
expr = Expression();
Match(SymbolType.RightParenthesis);
pn.AddStatement(new AssertNode(expr));
break;
default:
throw new Error($"Statement can not start with {this.token.SymbolType}", this.token);
}
}
